Piezoelectric/electrostrictive device and method of manufacturing same

ABSTRACT

A piezoelectric/electrostrictive device comprises a pair of mutually opposing thin plate sections, a movable section, and a fixation section for supporting the thin plate sections and the movable section. Piezoelectric/electrostrictive elements are arranged on the pair of thin plate sections. A hole is formed by the inner walls of the pair of thin plate sections, an inner wall of the movable section, and an inner wall of the fixation section. A through-hole having a rectangular cross section is formed over a range from a forward end surface of the movable section to the hole to realize a light weight of the movable section.

CROSS REFERENCE TO A RELATED APPLICATION

[0001] This application is a division of U.S. patent application Ser.No. 09/61 3,536, filed Jul. 10, 2000, now allowed, the entirety of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a piezoelectric/electrostrictivedevice which is provided with a movable section to be operated on thebasis of a displacement action of a piezoelectric/electrostrictiveelement, or a piezoelectric/electrostrictive device which is capable ofdetecting displacement of a movable section by the aid of apiezoelectric/electrostrictive element, and a method for producing thesame. In particular, the present invention relates to apiezoelectric/electrostrictive device which is excellent in strength,shock resistance, and moisture resistance and which makes it possible toefficiently operate a movable section to a great extent, and a methodfor producing the same.

[0004] 2. Description of the Related Art

[0005] Recently, it is desirable to realize a displacement element thatmakes it possible to adjust an optical path length and position in anorder of submicron, for example, in the fields of optics, magneticrecording, and precision machining. The development for such adisplacement element is advanced and is based on the use of thedisplacement brought about by an inverse piezoelectric effect or anelectrostrictive effect caused when a voltage is applied to apiezoelectric/electrostrictive material (for example, a ferroelectricmaterial).

[0006] As shown in FIG. 44, for example, those hitherto disclosed assuch a displacement element include a piezoelectric actuator comprisinga fixation section 204, a movable section 206, and a beam section 208for supporting the fixation and movable sections. The displacementelement is formed in an integrated manner with a hole 202 providedthrough a plate-shaped member 200 composed of apiezoelectric/electrostrictive material and with an electrode layer 210provided on the beam section (see, for example, Japanese Laid-OpenPatent Publication No. 10-136665).

[0007] The piezoelectric actuator is operated such that when a voltageis applied to the electrode layer 210, the beam section 208 makesexpansion and contraction in a direction along a line obtained byconnecting the fixation section 204 and the movable section 206 inaccordance with the inverse piezoelectric effect or the electrostrictiveeffect. Therefore, the movable section 206 can perform a circulararc-shaped displacement or a rotational displacement in the plane of theplate-shaped member 200.

[0008] On the other hand, Japanese Laid-Open Patent Publication No.63-64640 discloses a technique in relation to an actuator based on theuse of a bimorph. In this technique, electrodes for the bimorph areprovided in a divided manner. The actuator is driven due to theselection of the divided electrodes, and thus, a highly accuratepositioning is performed at a high speed. This patent document(especially in FIG. 4) discloses a structure in which, for example, twobimorphs are used in an opposed manner.

[0009] However, the piezoelectric actuator described above involves sucha problem that the amount of operation of the movable section is small,because the displacement in the direction of expansion and contractionof the piezoelectric/electrostrictive material (i.e., in the in-planedirection of the plate-shaped member) is transmitted to the movablesection as it is.

[0010] All of the parts of the piezoelectric actuator are made of apiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the following problemsarise. That is, the mechanical strength is low, and the piezoelectricactuator is inferior in handling performance, shock resistance, andmoisture resistance. Further, the piezoelectric actuator itself isheavy, and its operation tends to be affected by harmful vibrations (forexample, residual vibration and noise vibration during high speedoperation).

[0011] In order to solve the problems described above, it has beensuggested that a filler material having flexibility is supplied to ahole included in the device. However, it is clear that a decreasedamount of displacement resulting from the inverse piezoelectric effector the electrostrictive effect remains in effect, even when the fillermaterial is supplied to the above-mentioned hole.

[0012] On the other hand, FIG. 4 in Japanese Laid-Open PatentPublication No. 63-64640 resides in the junction of a mediating memberand a bimorph in which the mediating member is joined with the portionat which no divided electrode exists. The effect of the dividedelectrode cannot be utilized at the joined portion. That is, thejunction is merely made at the bimorph portion which is not thedisplacement-generating section. A similar form is adopted for thejunction of the head and the bimorph.

[0013] As a result, the following structure is brought about. That is, abending displacement of the bimorph is expressed toward an internalspace between the mediating member and the head. Therefore, it isimpossible to effectively displace the head itself with respect to theexternal space.

[0014] in many cases, the conventional devices of this type have such astructure rendering it difficult to realize a high resonance frequencyrequired for a high speed operation, or such devices have such astructure rendering it impossible to increase the displacement of themovable section. Consequently, the following contradicting structure isobtained. That is, whenever a high resonance frequency is desired, thedisplacement amount of the movable section is sacrificed. On the otherhand, whenever the displacement amount of the movable section isincreased, it is impossible to achieve the realization of a highresonance frequency.

SUMMARY OF INVENTION

[0015] The present invention has been made taking the foregoing problemsinto consideration. An object of the present invention is to provide apiezoelectric/electrostrictive device and a method for producing thesame which make it possible to obtain a displacement element that isscarcely affected by harmful vibrations during its operation. Anotherobject is to provide a device capable of achieving a high speed responsewith a high mechanical strength while being excellent in handlingperformance, shock resistance, and moisture resistance. A further objectis to provide a device wherein a movable section can be greatlydisplaced with a high speed of the displacement action and thus,realizing a high resonance frequency. Yet another object is to provide asensor element which makes it possible to accurately detect a vibrationof the movable section.

[0016] According to the present invention, there is provided apiezoelectric/electrostrictive device comprising a pair of mutuallyopposing thin plate sections, a movable section, and a fixation sectionfor supporting the thin plate sections and the movable section. One ormore piezoelectric/electrostrictive elements is arranged on at least oneof the thin plate sections. A hole is formed by the inner walls of thepair of thin plate sections, an inner wall of the movable section, andan inner wall of the fixation section. The movable section has a cutoutportion. It is also preferable that the cutout portion includes a hollowsection and/or a through-hole provided for the movable section.

[0017] Accordingly, the movable section is allowed to have a lightweight owing to the presence of the cutout. Therefore, it is possible toincrease the resonance frequency without decreasing the displacementamount of the movable section. Further, it is possible to appropriatelydecrease the rigidity of the movable section. Therefore, an advantage isobtained such that the displacement amount of the movable section can beincreased. When the thin plate section, the movable section, and thefixation section are integrated into one unit, it is unnecessary toconstruct all parts with the piezoelectric/electrostrictive materialwhich is a fragile material having a relatively heavy weight. Therefore,an advantage is obtained such that the mechanical strength is high whilebeing excellent in handling performance, shock resistance, and moistureresistance, and the operation is scarcely affected by harmful vibration(for example, residual vibration and noise vibration during high speedoperation).

[0018] According to another aspect of the present invention, there isprovided a piezoelectric/electrostrictive device comprising a pair ofmutually opposing thin plate sections, a movable section, and a fixationsection for supporting the thin plate sections and the movable section;one or more piezoelectric/electrostrictive elements arranged on at leastone thin plate section of the pair of thin plate sections; and a holeformed by both inner walls of the pair of thin plate sections, an innerwall of the movable section, and an inner wall of the fixation section;wherein a part of the inner wall of the movable section is expanded inthe hole.

[0019] Accordingly, for example, when a part is attached to the movablesection, it is possible to increase the areal size of a part attachmentsurface of the movable section, without changing the maximum length ofthe piezoelectric/electrostrictive device. Thus, it is possible toimprove the reliability concerning the attachment of the part.

[0020] Further, the weight is increased, because the expanded section isprovided. However, the expanded section is expanded toward the hole.Therefore, the center of gravity of the movable section can be locatedat a position deviated toward the fixation section. Any influence ishardly exerted by the decrease in resonance frequency caused by theincrease in weight. In this arrangement, the part is also attached at aposition deviated toward the fixation section. Therefore, the resonancefrequency is scarcely decreased after the part is attached. Thedisplacement of the movable section is not decreased as well. That is,the device is designed such that the resonance frequency issubstantially improved.

[0021] In other words, according to the present invention, the degree ofthe influence on the resonance frequency (decrease in resonancefrequency), which would be otherwise enhanced when much weight is givento the attachment of the part, can be decreased, while enlarging theareal size of the part attachment surface of the movable section, andimproving the reliability concerning the attachment of the part.

[0022] In the present invention, it is also preferable that a cutout isprovided for the movable section. Accordingly, it is possible tosimultaneously realize a light weight of the movable section and anincrease in the displacement amount of the movable section. Thus, it ispossible to simultaneously achieve the mutually contradicting“realization of the high resonance frequency” and the “increase indisplacement”.

[0023] Further, it is also preferable that a part of the inner wall ofthe movable section is expanded to the hole. Accordingly, it is possibleto realize the “reliability of the part attachment” in addition to the“realization of the high resonance frequency” and the “increase indisplacement”.

[0024] In the invention described above, it is also preferable that themovable section is constructed to have a main movable section body and aportion which is provided for at least one surface of the main movablesection body and which has an areal size larger than that of the mainmovable section body. When the portion, which has the areal size largerthan that of the main movable section body, is utilized to attach thepart, then it is possible to contemplate the reliability of the partattachment, and it is possible to enhance the reliability concerning theoperation.

[0025] In the invention described above, the movable section, thefixation section, and the thin plate sections may be made of ceramics ormetal. Alternatively, each of the components may be made of a ceramicmaterial, or each of them may be made of a metal material. Further, eachof the components may be constructed to have a hybrid structure obtainedby combining those produced from materials of ceramics and metal.

[0026] It is also preferable that the thin plate sections, the movablesection, and the fixation section are composed of a ceramic substrateobtained by being integrated into one unit by simultaneously sintering aceramic green laminate and cutting off unnecessary portions. It is alsopreferable that the piezoelectric/electrostrictive element has afilm-shaped configuration, and it is integrated with the ceramicsubstrate by means of sintering.

[0027] In this arrangement, the piezoelectric/electrostrictive elementmay be constructed to have a piezoelectric/electrostrictive layer and apair of electrodes formed on the piezoelectric/electrostrictive layer.Further, the piezoelectric/electrostrictive element may have apiezoelectric/electrostrictive layer and a pair of electrodes formed onboth sides of the piezoelectric/electrostrictive layer, and oneelectrode of the pair of electrodes may be formed on at least the thinplate section. In this arrangement, the vibration caused by thepiezoelectric/electrostrictive element can be efficiently transmitted tothe movable section or the fixation section via the thin plate section.

[0028] Accordingly, it is possible to improve the response performance.Especially, it is preferable that the piezoelectric/electrostrictiveelement is constructed in a stacked form comprising a plurality of thepiezoelectric/electrostrictive layers and the electrodes.

[0029] When the arrangement as described above is adopted, the followingfeatures are obtained. That is, the force generated by thepiezoelectric/electrostrictive element is increased. Accordingly, it ispossible to obtain the large displacement. Further, owing to theincrease in rigidity of the device itself, it is possible to realize thehigh resonance frequency, and it is easy to achieve the realization ofthe high speed of the displacement operation.

[0030] In the invention described above, it is also preferable that thehole is filled with a gel material. In this arrangement, although thedisplacement action of the movable section is restricted due to thepresence of the filler material in ordinary cases, the inventiondescribed above intends to reduce the weight as a result of theformation of the cutout for the movable section, and increase thedisplacement amount of the movable section. Therefore, the restrictionof the displacement action of the movable section by the filler materialis counteracted, and it is possible to realize the effect owing to thepresence of the filler material, i.e., the realization of the highresonance frequency and the maintenance of the rigidity.

[0031] According to still another aspect of the present invention, thereis provided a method for producing a piezoelectric/electrostrictivedevice comprising a pair of mutually opposing thin plate sections, amovable section, and a fixation section for supporting the thin platesections and the movable section; one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; and a hole formed byboth inner walls of the pair of thin plate sections, an inner wall ofthe movable section, and an inner wall of the fixation section; themethod comprising a step of forming the movable section having a cutoutby cutting off a predetermined part after producing at least thepiezoelectric/electrostrictive element on the thin plate section.

[0032] In still another aspect, the present invention preferably lies ina method comprising a step of producing a ceramic laminate by integrallysintering a ceramic green laminate including at least a ceramic greensheet having a window for forming at least the hole thereafter andceramic green sheets to be formed into the thin plate sectionsthereafter to produce the ceramic laminate; a step of forming thepiezoelectric/electrostrictive element on an outer surface of a portionof the ceramic laminate to be formed into the thin plate section; and acutoff step of forming the movable section having at least a cutout bymeans of at least one time of cutoff treatment for the ceramic laminateformed with the piezoelectric/electrostrictive element.

[0033] Accordingly, the movable section is allowed to have a lightweight owing to the presence of the cutout. It is possible toefficiently and easily produce the piezoelectric/electrostrictive devicewhich makes it possible to increase the resonance frequency withoutdecreasing the displacement amount of the movable section. It ispossible to realize mass production of the high performancepiezoelectric/electrostrictive device.

[0034] The phrase “after producing the piezoelectric/electrostrictiveelement” referred to herein indicates a state in which at least thepiezoelectric/electrostrictive layer is formed. As for the electrode tobe formed after the formation of the piezoelectric/electrostrictivelayer, the electrode may be formed after performing the cutoff to formthe movable section having the cutout.

[0035] It is also preferable that in the step of producing the ceramiclaminate, the ceramic laminate is produced by integrally sintering aceramic green laminate including a ceramic green sheet having a windowfor forming the movable section having at least the cutout, and theceramic green sheets to be formed into the thin plate sectionsthereafter to produce the ceramic laminate; and in the cutoff step, themovable section having at least the cutout is formed by means of thecutoff treatment for the ceramic laminate formed with thepiezoelectric/electrostrictive element.

[0036] It is also preferable that the cutout includes a hollow sectionand/or a through-hole provided for the movable section.

[0037] According to still another aspect of the present invention, thereis provided a method for producing a piezoelectric/electrostrictivedevice comprising a pair of mutually opposing thin plate sections, amovable section, and a fixation section for supporting the thin platesections and the movable section; one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; and a hole formed bythe inner walls of the pair of thin plate sections, an inner wall of themovable section, and an inner wall of the fixation section; the methodcomprising a step of forming the movable section having an expandedsection expanded in the hole by cutting off a predetermined part afterproducing at least the piezoelectric/electrostrictive element on thethin plate section.

[0038] In still another aspect, the present invention preferably lies ina method comprising a step of producing a ceramic laminate by integrallysintering a ceramic green laminate including at least a ceramic greensheet having a window for forming at least the hole thereafter andceramic green sheets to be formed into the thin plate sectionsthereafter to produce the ceramic laminate; a step of forming thepiezoelectric/electrostrictive element on an outer surface of a portionof the ceramic laminate to be formed into the thin plate section; and acutoff step of forming the movable section having at least an expandedsection expanded in the hole by means of at least one time of cutofftreatment for the ceramic laminate formed with thepiezoelectric/electrostrictive element.

[0039] Accordingly, it is possible to efficiently and easily produce thepiezoelectric/electrostrictive device which makes it possible todecrease the degree of the influence on the resonance frequency(decrease in resonance frequency), while increasing the areal size ofthe part attachment surface of the movable section.

[0040] It is also preferable that in the step of producing the ceramiclaminate, the ceramic laminate is produced by integrally sintering aceramic green laminate including a ceramic green sheet having a windowfor forming the movable section formed with at least an expandedsection, and the ceramic green sheets to be formed into the thin platesections thereafter to produce the ceramic laminate; and in the cutoffstep, the movable section having at least an expanded section is formedby means of the cutoff treatment for the ceramic laminate formed withthe piezoelectric/electrostrictive element.

[0041] It is also preferable for the production methods described abovethat in the cutoff step, the hole is simultaneously exposed by means ofthe cutoff treatment for the ceramic laminate. In this process, theformation of the movable section having the cutout may be performedsimultaneously with the formation of the hole. There is no limitationfor the sequence to perform the formation steps.

[0042] Therefore, the piezoelectric/electrostrictive device according tothe present invention can be utilized as the active device including,for example, various transducers, various actuators, frequency regionfunctional parts (filters), transformers, vibrators, resonators,oscillators, and discriminators for communication and power generationapplications, as well as the sensor element for various sensorsincluding, for example, ultrasonic sensors, acceleration sensors,angular velocity sensors, shock sensors, and mass sensors. Especially,the piezoelectric/electrostrictive device according to the presentinvention can be preferably utilized for various actuators to be usedfor a mechanism for adjusting the displacement and the positioning andfor adjusting the angle for various precision parts such as those ofoptical instruments and precision mechanical equipments.

[0043] The above and other objects, features, and advantages of thepresent invention will become more apparent from the followingdescription when taken in conjunction with the accompanying drawings inwhich a preferred embodiment of the present invention is shown by way ofillustrative example.

BRIEF DESCRIPTION OF DRAWINGS

[0044]FIG. 1 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a first embodiment;

[0045]FIG. 2 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a first modifiedembodiment;

[0046]FIG. 3 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a second modifiedembodiment;

[0047]FIG. 4 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a third modifiedembodiment;

[0048]FIG. 5 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a fourth modifiedembodiment;

[0049]FIG. 6 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a fifth modifiedembodiment;

[0050]FIG. 7 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a sixth modifiedembodiment;

[0051]FIG. 8 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a seventh modifiedembodiment;

[0052]FIG. 9 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to an eighth modifiedembodiment;

[0053]FIG. 10 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a ninth modifiedembodiment;

[0054]FIG. 11 shows, with partial omission, another embodiment of thepiezoelectric/electrostrictive element;

[0055]FIG. 12 shows, with partial omission, still another embodiment ofthe piezoelectric/electrostrictive element;

[0056]FIG. 13 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a tenth modifiedembodiment;

[0057]FIG. 14 illustrates a situation in which both of thepiezoelectric/electrostrictive elements do not make the displacementaction in the piezoelectric/electrostrictive device according to thefirst embodiment;

[0058]FIG. 15A shows a waveform illustrating a voltage waveform to beapplied to the first piezoelectric/electrostrictive element;

[0059]FIG. 15B shows a waveform illustrating a voltage waveform to beapplied to the second piezoelectric/electrostrictive element;

[0060]FIG. 16 illustrates a situation in which thepiezoelectric/electrostrictive element makes the displacement action inthe piezoelectric/electrostrictive device according to the firstembodiment;

[0061]FIG. 17A illustrates a process for laminating ceramic green sheetsrequired when the piezoelectric/electrostrictive device according to thefirst embodiment is produced in accordance with a first productionmethod;

[0062]FIG. 17B illustrates a state in which a ceramic green laminate isformed;

[0063]FIG. 18 illustrates a state in which the ceramic green laminate issintered into a ceramic laminate, and then apiezoelectric/electrostrictive element is formed on the ceramiclaminate;

[0064]FIG. 19 illustrates a state in which the ceramic laminate is cutalong predetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the first embodiment;

[0065]FIG. 20A illustrates a process for laminating ceramic green sheetsrequired when the piezoelectric/electrostrictive device according to aneleventh modified embodiment is produced in accordance with a secondproduction method;

[0066]FIG. 20B illustrates a state in which a ceramic green laminate isformed;

[0067]FIG. 21A illustrates a state in which the ceramic green laminateis sintered into a ceramic laminate;

[0068]FIG. 21B illustrates a state in whichpiezoelectric/electrostrictive elements, which are constructed asseparate members, are bonded to surfaces of metal plates to serve asthin plate sections respectively;

[0069]FIG. 22 illustrates a state in the second production method inwhich the metal plate is bonded to the ceramic laminate to provide ahybrid laminate;

[0070]FIG. 23 illustrates a state in the second production method inwhich the hybrid laminate is cut along predetermined cutting lines toprovide the piezoelectric/electrostrictive device according to theeleventh modified embodiment;

[0071]FIG. 24A illustrates a state in a third production method in whicha ceramic green laminate is sintered into a ceramic laminate;

[0072]FIG. 24B illustrates a state in whichpiezoelectric/electrostrictive elements, which are constructed asseparate members, are bonded to surfaces of metal plates to serve asthin plate sections respectively;

[0073]FIG. 25 illustrates a state in the third production method inwhich the metal plate is bonded to the ceramic laminate to provide ahybrid laminate;

[0074]FIG. 26 illustrates a state in the third production method inwhich the hybrid laminate is cut along predetermined cutting lines toprovide a piezoelectric/electrostrictive device according to a twelfthmodified embodiment;

[0075]FIG. 27 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a second embodiment;

[0076]FIG. 28A illustrates a process for laminating ceramic green sheetsrequired when the piezoelectric/electrostrictive device according to thesecond embodiment is produced in accordance with the first productionmethod;

[0077]FIG. 28B illustrates a state in which a ceramic green laminate isformed;

[0078]FIG. 29 illustrates a state in which the ceramic green laminate issintered into a ceramic laminate, and then thepiezoelectric/electrostrictive element is formed on the ceramiclaminate;

[0079]FIG. 30 illustrates a state in which the ceramic laminate is cutalong predetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the secondembodiment;

[0080]FIG. 31 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a third embodiment;

[0081]FIG. 32 shows a perspective view illustrating an arrangement of amodified embodiment of the piezoelectric/electrostrictive deviceaccording to the third embodiment;

[0082]FIG. 33 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a fourth embodiment;

[0083]FIG. 34A illustrates a process for laminating ceramic green sheetsrequired when the piezoelectric/electrostrictive device according to thefourth embodiment is produced in accordance with the first productionmethod;

[0084]FIG. 34B illustrates a state in which a ceramic green laminate isformed;

[0085]FIG. 35 illustrates a state in which the ceramic green laminate issintered into a ceramic laminate, and then thepiezoelectric/electrostrictive element is formed on the ceramiclaminate;

[0086]FIG. 36 illustrates a state in which the ceramic laminate is cutalong predetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the fourthembodiment;

[0087]FIG. 37 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a fifth embodiment;

[0088]FIG. 38 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a sixth embodiment;

[0089]FIG. 39A illustrates a process for laminating ceramic green sheetsrequired when the piezoelectric/electrostrictive device according to thesixth embodiment is produced in accordance with the first productionmethod;

[0090]FIG. 39B illustrates a state in which a ceramic green laminate isformed;

[0091]FIG. 40 illustrates a state in which the ceramic green laminate issintered into a ceramic laminate, and then thepiezoelectric/electrostrictive element is formed on the ceramiclaminate;

[0092]FIG. 41 illustrates a state in which the ceramic laminate is cutalong predetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the sixth embodiment;

[0093]FIG. 42 shows a perspective view illustrating an arrangement of amodified embodiment of the piezoelectric/electrostrictive deviceaccording to the sixth embodiment;

[0094]FIG. 43 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a seventh embodiment;and

[0095]FIG. 44 shows an arrangement of a piezoelectric/electrostrictivedevice concerning an illustrative conventional technique.

DETAILED DESCRIPTION

[0096] Explanation will be made below with reference to FIGS. 1 to 43for illustrative embodiments of the piezoelectric/electrostrictivedevice and the production method for the same according to the presentinvention.

[0097] It is noted that the piezoelectric/electrostrictive device of thepresent invention includes a piezoelectric/electrostrictive element formutually converting electrical energy and mechanical energy. Therefore,the piezoelectric/electrostrictive device is most preferably used as anactive element for various actuators and vibrators. It is especiallyemployed as a displacement element based on the use of the displacementbrought about by the inverse piezoelectric effect and theelectrostrictive effect. Additionally, thepiezoelectric/electrostrictive device is also preferably used as apassive element such as acceleration sensor elements and shock sensorelements.

[0098] As shown in FIG. 1, the piezoelectric/electrostrictive device 10Aaccording to this embodiment has a substrate 14 which has a lengthyrectangular parallelepiped-shaped configuration and a hole 12 providedat an approximately central portion in the major axis direction thereof.

[0099] The substrate 14 comprises a pair of mutually opposing thin platesections 16 a, 16 b, a movable section 20, and a fixation section 22 forsupporting the pair of thin plate sections 16 a, 16 b and the movablesection 20. Piezoelectric/electrostrictive elements 24 a, 24 b areformed on parts of at least the thin plate sections 16 a, 16 b,respectively.

[0100] The following definition is made for the perspective viewsincluding, for example, FIG. 1. That is, concerning the movable section20 and the fixation section 22, the surface disposed and viewed at thefront is defined to be a “front surface”, and the surface disposed atthe back is defined to be a “back surface”. Further, concerning themovable section 20 and the fixation section 22, the surfaces, which arecontinuous to the upper surfaces of the thin plate sections 16 a, 16 b(surfaces on which the piezoelectric/electrostrictive elements 24 a, 24b are formed), are defined to be “side surfaces”.

[0101] Those usable as the substrate 14 include a structure comprisingceramic or metal materials as a whole, or a hybrid structure obtained bycombining products produced with materials of ceramics and metals.

[0102] Those adoptable for the substrate 14 include, for example, astructure in which respective parts are bonded to one another with anadhesive such as an organic resin or a glass material or the like. Anintegrated ceramic structure is obtained by sintering and integrating aceramic green laminate into one unit. An integrated metal structure isobtained, for example, by brazing, soldering, eutectic bonding, orwelding into one unit. Preferably, it is desirable to construct thesubstrate 14 with a ceramic laminate integrated into one unit bysintering a ceramic green laminate.

[0103] The time-dependent change of state scarcely occurs in theintegrated product of ceramic, because no adhesive exists at joinedportions between the respective parts. Therefore, the reliability of thejoined portion is high, giving a structure which is advantageous toensure the proper rigidity. Additionally, the integrated product ofceramic can be easily produced with the method for laminating ceramicgreen sheets (described below).

[0104] The piezoelectric/electrostrictive elements 24 a, 24 b areprepared as separate members (described below), and the preparedpiezoelectric/electrostrictive elements 24 a, 24 b are affixed to thesubstrate 14 with an adhesive such as organic resin or glass or by meansof, for example, brazing, soldering, or eutectic bonding. Alternatively,the piezoelectric/electrostrictive elements 24 a, 24 b may be directlyformed on the substrate 14 through the use of a film formation method.

[0105] The piezoelectric/electrostrictive device 10A includes a hole 12having, for example, a rectangular configuration which is formed by theinner walls of the pair of thin plate sections 16 a, 16 b, an inner wall20 a of the movable section 20, and an inner wall 22 a of the fixationsection 22. The piezoelectric/electrostrictive device 10A operates todisplace the movable section 20 in accordance with the driving of eitheror both of the piezoelectric/electrostrictive elements 24 a and 24 b.The piezoelectric/electrostrictive device 10A is also fabricated todetect the displacement of the movable section 20 through a sensingfunction of either or both of the piezoelectric/electrostrictiveelements 24 a and 24 b.

[0106] Each of the piezoelectric/electrostrictive elements 24 a, 24 bcomprises a piezoelectric/electrostrictive layer 26, and a pair ofelectrodes 28, 30 formed on both sides of thepiezoelectric/electrostrictive layer 26. One electrode (i.e., numeral 28in FIG. 1) of the pair of electrodes 28, 30 is formed on at least eachof the pair of the thin plate sections 16 a, 16 b.

[0107] In the embodiment shown in FIG. 1, respective forward endsurfaces of the pair of electrodes 28, 30 and thepiezoelectric/electrostrictive layer 26 (employed to construct thepiezoelectric/electrostrictive elements 24 a, 24 b) are substantiallyaligned. A substantial driving portion 18 of thepiezoelectric/electrostrictive element 24 a, 24 b (portion at which thepair of electrodes 28, 30 are overlapped with each other with thepiezoelectric/electrostrictive layer 26 interposed therebetween) iscontinuously formed over a range from a part of the outercircumferential surface of the fixation section 22 to a part of theouter circumferential surface of the thin plate section 16 a, 16 b.Especially, in this embodiment, the respective forward end surfaces ofthe pair of electrodes 28, 30 are located at the positions slightlydeviated rearwardly from the inner wall 20 a of the movable section 20.Of course, the piezoelectric/electrostrictive elements 24 a, 24 b may beformed such that the substantial driving portion 18 is located over arange from a part of the movable section 20 to a part of the thin platesection 16 a, 16 b.

[0108] A voltage is applied to the pair of electrodes 28, 30 viaterminals (pads) 32, 34 of the respective electrodes 28, 30 formed onboth side surfaces (element formation surfaces) of the fixation section22 respectively. The respective terminals 32, 34 are positioned asfollows. That is, the terminal 32 corresponding to the first electrode28 is formed at a position deviated toward the rearward end of thefixation section 22. The terminal 34 corresponding to the secondelectrode 30 (disposed on the side of the external space) is formed at aposition deviated toward the inner wall 22 a of the fixation section 22.

[0109] In this embodiment, the piezoelectric/electrostrictive device 10Acan be individually fixed by utilizing the surfaces that arerespectively different from the surfaces on which the terminals 32, 34are arranged. As a result, it is possible to obtain a high reliabilityfor both of the fixation of the piezoelectric/electrostrictive device10A and the electric connection between the circuit and the terminals32, 34. In this arrangement, the electric connection between theterminals 32, 34 and the circuit is made, for example, by means of aflexible printed circuit (also referred to as FPC), a flexible flatcable (also referred to as FFC), and a wire bonding.

[0110] As shown in FIG. 1, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment is constructed such that a cutout 36is formed in the movable section 20. In the embodiment shown in FIG. 1,the cutout 36 is a through-hole having a rectangular cross section whichis formed continuously over a range from the forward end surface of themovable section 20 to the hole 12.

[0111] Structures other than the structure shown in FIG. 1 are availablefor use in the arrangement of the piezoelectric/electrostrictiveelements 24 a, 24 b. That is, as in a piezoelectric/electrostrictivedevice 10Aa according to a first modified embodiment shown in FIG. 2, itis also preferable that while the respective forward ends of the pair ofelectrodes 28, 30 (employed to construct thepiezoelectric/electrostrictive elements 24 a, 24 b) are substantiallyaligned, only the forward end of the piezoelectric/electrostrictivelayer 26 is allowed to protrude toward the movable section 20.Alternatively, as in a piezoelectric/electrostrictive device 10Abaccording to a second modified embodiment shown in FIG. 3, it is alsopreferable that the respective forward ends of the first electrode 28and the piezoelectric/electrostrictive layer 26 are aligned, and onlythe forward end of the second electrode 30 is disposed at a positiondeviated toward the fixation section 22.

[0112] Alternatively, as in a piezoelectric/electrostrictive device 10Acaccording to a third modified embodiment shown in FIG. 4, it is alsopreferable that the respective forward ends of the first electrode 28and the piezoelectric/electrostrictive layer 26 are allowed to extend upto the side surface of the movable section 20, and the forward end ofthe second electrode 30 is located at an approximately central portionin a length direction (i.e., the Z axis direction) of the thin platesection 16 a, 16 b.

[0113] In the embodiments described above, thepiezoelectric/electrostrictive elements 24 a, 24 b are constructed withthe piezoelectric/electrostrictive layer 26 having a one-layeredstructure and a pair of electrodes 28, 30. Alternatively, it is alsopreferable that the piezoelectric/electrostrictive elements 24 a, 24 bare constructed in a stacked form composed of a plurality of thepiezoelectric/electrostrictive layers 26 and the electrodes 28, 30.

[0114] For example, as in a piezoelectric/electrostrictive device 10Adaccording to a fourth modified embodiment shown in FIG. 5, each of thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 resides in a multilayered structure. The first electrodes 28 and thesecond electrodes 30 are alternately stacked with each other to providethe piezoelectric/electrostrictive element 24 a, 24 b which has amultiple stage structure at a portion (substantial driving portion 18)at which the first electrodes 28 and the second electrodes 30 areoverlapped with each other with the piezoelectric/electrostrictive layer26 interposed therebetween. FIG. 5 is illustrative of the followingcase. That is, the piezoelectric/electrostrictive layer 26 has athree-layered structure. The first electrodes 28 are formed in aseparate manner respectively on the lower surface of the first layer(side surface of the thin plate section 16 a, 16 b) and on the uppersurface of the second layer. The second electrodes 30 are formed in aseparate manner respectively on the upper surface of the first layer andon the upper surface of the third layer. Further, terminals 32 a, 32 bare provided on respective ends of the first electrodes 28 respectively,and terminals 34 a, 34 b are provided on respective ends of the secondelectrodes 30 respectively.

[0115] As in a piezoelectric/electrostrictive device 10Ae according to afifth modified embodiment shown in FIG. 6, each of thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 resides in a multilayered structure. The first electrode 28 and thesecond electrode 30 are alternately stacked with each other so that asubstantially comb-shaped configuration is obtained in a cross sectionto provide the piezoelectric/electrostrictive element 24 a, 24 b whichhas a multiple stage structure at a portion (substantial driving portion18) at which the first electrode 28 and the second electrode 30 areoverlapped with each other with the piezoelectric/electrostrictive layer26 interposed therebetween.

[0116]FIG. 6 is illustrative of the following case. That is, thepiezoelectric/electrostrictive layer 26 has a three-layered structure.The first electrode 28 is formed in a comb-shaped configuration to belocated on the lower surface of the first layer (side surface of thethin plate section 16 a, 16 b) and on the upper surface of the secondlayer. The second electrode 30 is formed in a comb-shaped configurationto be located on the upper surface of the first layer and on the uppersurface of the third layer. In the case of this structure, each of thefirst electrode 28 and the second electrode 30 is continuous and common.Accordingly, it is possible to decrease the number of terminals 32, 34as compared with the structure shown in FIG. 5. Therefore, it ispossible to suppress the increase in size which would be otherwiseinvolved in the multilayered structure of thepiezoelectric/electrostrictive element 24 a, 24 b.

[0117] When the number of stages is increased, it is possible toincrease the driving force. However, the electric power consumption isalso increased in accordance therewith. Therefore, when the device ispractically produced and used, for example, it is preferable that thenumber of stages is appropriately determined depending on the way of useand the state of use. In the case of the piezoelectric/electrostrictivedevice 10Ae according to the fifth modified embodiment, even when thedriving force is increased by providing the multiple stage structure ofthe piezoelectric/electrostrictive element 24 a, 24 b, the width of thethin plate section 16 a, 16 b (distance in the Y axis direction) isbasically unchanged. Therefore, the device is extremely preferred foruse in applications, for example, employing an actuator for the purposeof a ringing control and the positioning of a magnetic head for a harddisk to be used in an extremely narrow gap.

[0118] Alternatively, as in a piezoelectric/electrostrictive device 10Afaccording to a sixth modified embodiment shown in FIG. 7, it is alsopreferable that two piezoelectric/electrostrictive elements 24 a 1, 24 b1 having a multiple stage structure are formed to extend over thefixation section 22 and the thin plate section 16 a, 16 b respectively,and another two piezoelectric/electrostrictive elements 24 a 2, 24 b 2having a multiple stage structure are formed to extend over the movablesection 20 and the thin plate section 16 a, 16 b respectively. In thisarrangement, the movable section 20 can be displaced extremely greatlyowing to the effect that the piezoelectric/electrostrictive element 24a, 24 b has the multiple stage structure and the effect that the numberof points of action to displace the movable section 20 is increased.Additionally, the piezoelectric/electrostrictive device 10Af isexcellent in high speed response performance, which is preferred.

[0119] Alternatively, as in a piezoelectric/electrostrictive device 10Agaccording to a seventh modified embodiment shown in FIG. 8, it is alsopreferable to form the piezoelectric/electrostrictive element 24 a, 24 bso that the forward end thereof stays on the thin plate section 16 a, 16b. FIG. 8 is illustrative of the case in which the forward end of thepiezoelectric/electrostrictive element 24 a, 24 b is located at asubstantially central portion in the length direction of the thin platesection 16 a, 16 b. This arrangement is advantageous in that the movablesection 20 can be displaced to a great extent substantially in parallelto the side surface direction (X axis direction).

[0120] Alternatively, as in a piezoelectric/electrostrictive device 10Ahaccording to an eighth modified embodiment shown in FIG. 9, it is alsopreferable that mutually opposing end surfaces 37 a, 37 b are formed forthe movable section 20. In this arrangement, the internal residualstress, which has been generated in the piezoelectric/electrostrictiveelements 24 a, 24 b and/or the thin plate sections 16 a, 16 b during theproduction, can be released by the movement of the end surfaces 37 a, 37b. Therefore, the displacement action of the movable section 20 is notinhibited by the internal residual stress. Thus, it is possible toobtain the displacement action of the movable section 20 substantiallyas designed. Additionally, the release of the stress makes it possibleto improve the mechanical strength of the piezoelectric/electrostrictivedevice 10Ah as well. The embodiment described above is illustrative ofthe case in which the mutually opposing end surfaces 37 a, 37 b areprovided for the movable section 20. Alternatively, the mutuallyopposing end surfaces 37 a, 37 b may be provided for the fixationsection 22.

[0121] Alternatively, as in a piezoelectric/electrostrictive device 10Aiaccording to a ninth modified embodiment shown in FIG. 10, it is alsopreferable that a pair of thin plate sections 16 a, 16 b are bent indirections to make separation from each other, and they are convextoward the outside. In this arrangement, high rigidity is exhibited forthe vibration (bending displacement) of the thin plate sections 16 a, 16b. As a result, it is possible to increase the resonance frequency ofthe vibration itself of the thin plate sections 16 a, 16 b. Thestructure, in which the thin plate sections 16 a, 16 b are previouslybent in the directions to make separation from each other, i.e., towardthe external space as described above, is a structure which is efficientto convert the displacement of the piezoelectric/electrostrictiveelements 24 a, 24 b into the displacement of the movable section 20 inthe direction toward the external space. Therefore, it is possible togreatly displace the movable section 20.

[0122] In other words, in the ninth modified embodiment, the rigidity ofthe thin plate sections 16 a, 16 b is enhanced, while the decrease indisplacement of the movable section 20, which is postulated from theincreased rigidity, is suppressed by providing the structure in whichthe thin plate sections 16 a, 16 b are allowed to protrude outwardly toincrease the conversion efficiency of the displacement. As a result, thestructure makes it possible to displace the movable section 20 at a highspeed to a great extent. Further, the structure described above alsoexhibits large durability against the force (external force) exerted onthe thin plate sections 16 a, 16 b from the outside. Therefore, thedevice is also excellent in strength.

[0123] The piezoelectric/electrostrictive element 24 a, 24 b describedabove is illustrative of the case of the construction of the so-calledsandwich structure in which the piezoelectric/electrostrictive layer 26is allowed to intervene between the pair of electrodes 28, 30.Alternatively, as shown in FIG. 11, a pair of comb-shaped electrodes 28,30 may be formed on the first principal surface of thepiezoelectric/electrostrictive layer 26 formed on at least the sidesurface of the thin plate section 16 a, 16 b. Further alternatively, asshown in FIG. 12, a pair of comb-shaped electrodes 28, 30 are formed andembedded in the piezoelectric/electrostrictive layer 26 formed on atleast the side surface of the thin plate section 16 a, 16 b.

[0124] The structure shown in FIG. 11 is advantageous in that it ispossible to suppress the electric power consumption to be low. Thestructure shown in FIG. 12 makes it possible to effectively utilize theinverse piezoelectric effect in the direction of the electric fieldhaving large generated force and strain, which is advantageous to causethe large displacement.

[0125] Specifically, the piezoelectric/electrostrictive element 24 a, 24b shown in FIG. 11 comprises the pair of electrodes 28, 30 having acomb-shaped structure formed on the first principal surface of thepiezoelectric/electrostrictive layer 26. In this structure, the firstelectrode 28 and the second electrode 30 are mutually opposed to oneanother in an alternate manner with a gap 29 having a constant widthinterposed therebetween. FIG. 11 is illustrative of the case in whichthe pair of electrodes 28, 30 are formed on the first principal surfaceof the piezoelectric/electrostrictive layer 26. Alternatively, the pairof electrodes 28, 30 may be formed between the thin plate section 16 a,16 b and the piezoelectric/electrostrictive layer 26. Furtheralternatively, the pair of comb-shaped electrodes 28, 30 may be formedon the first principal surface of the piezoelectric/electrostrictivelayer 26 and between the thin plate section 16 a, 16 b and thepiezoelectric/electrostrictive layer 26 respectively.

[0126] On the other hand, in the piezoelectric/electrostrictive element24 a, 24 b shown in FIG. 12, the pair of electrodes 28, 30 having acomb-shaped structure are formed so that they are embedded in thepiezoelectric/electrostrictive layer 26. In this structure, the firstelectrode 28 and the second electrode 30 are mutually opposed to oneanother in an alternate manner with a gap 29 having a constant widthinterposed therebetween.

[0127] The piezoelectric/electrostrictive elements 24 a, 24 b as shownin FIGS. 11 and 12 can be preferably used for thepiezoelectric/electrostrictive device 10A according to the firstembodiment as well. When the pair of comb-shaped electrodes 28, 30 areused as in the piezoelectric/electrostrictive elements 24 a, 24 b shownin FIGS. 11 and 12, the displacement of thepiezoelectric/electrostrictive element 24 a, 24 b can be increased bydecreasing the pitch D of the comb teeth of the respective electrodes28, 30.

[0128] Alternatively, as in a piezoelectric/electrostrictive device 10Ajaccording to a tenth modified embodiment shown in FIG. 13, it is alsopreferable that a partition 38 is provided between the cutout 36 and thehole 12. This arrangement provides an effect equivalent to that obtainedin the case in which the cutout 36 formed for the movable section 20 isthe through-hole (for example, see FIG. 1). Further, when variousmembers or parts are inserted into the cutout 36 to be fixed thereto,the member or the part is easily positioned by the aid of the partition38. It is possible to reduce the dispersion of the characteristic of thefinal product. Further, it is possible to utilize the five surfaces asthe bonding and fixing surface. Thus, the reliability is improvedconcerning the attachment of the member or the part.

[0129] The operation of the piezoelectric/electrostrictive device 10Aaccording to the first embodiment will now be explained. At first, forexample, when the two piezoelectric/electrostrictive elements 24 a, 24 bare in the natural state, namely when both of thepiezoelectric/electrostrictive elements 24 a, 24 b do not make thedisplacement action, then the major axis m of thepiezoelectric/electrostrictive device 10A (major axis of the fixationsection 22) is substantially coincident with the central axis n of themovable section 20 as shown in FIG. 14.

[0130] Starting from this state, for example, a sine wave Wa, which hasa predetermined bias electric potential Vb, is applied to the pair ofelectrodes 28, 30 of the first piezoelectric/electrostrictive element 24a as shown in a waveform figure shown in FIG. 15A, while a sine wave Wb,which has a phase different from that of the sine wave Wa by about 180°,is applied to the pair of electrodes 28, 30 of the secondpiezoelectric/electrostrictive element 24 b as shown in FIG. 15B.

[0131] The piezoelectric/electrostrictive layer 26 of the firstpiezoelectric/electrostrictive element 24 a makes the contractiondisplacement in the direction of the first principal surface at a stageat which, for example, a voltage having a maximum value is applied tothe pair of electrodes 28, 30 of the firstpiezoelectric/electrostrictive element 24 a. Accordingly, as shown inFIG. 16, for example, the stress is generated for the first thin platesection 16 a to bend the thin plate section 16 a, for example, in therightward direction as shown by the arrow A. Therefore, the first thinplate section 16 ais bent in the rightward direction. At this time, astate is given, in which no voltage is applied to the pair of electrodes28, 30 of the second piezoelectric/electrostrictive element 24 b.Therefore, the second thin plate section 16 b follows the bending of thefirst thin plate section 16 a, and it is bent in the rightwarddirection. As a result, the movable section 20 is displaced, forexample, in the rightward direction with respect to the major axis m ofthe piezoelectric/electrostrictive device 10A. The displacement amountis changed depending on the maximum value of the voltage applied to eachof the piezoelectric/electrostrictive elements 24 a, 24 b. For example,the larger the maximum value is, the larger the displacement amount is.

[0132] Especially, when a material having coercive electric field isapplied as the constitutive material for thepiezoelectric/electrostrictive layer 26, it is also preferable that thebias electric potential is adjusted so that the level of the minimumvalue is a slightly negative level as depicted by waveforms indicated bydashed lines in FIGS. 15A and 15B. In this case, for example, thestress, which is in the same direction as the bending direction of thefirst thin plate section 16 a, is generated in the second thin platesection 16 b by driving the piezoelectric/electrostrictive element (forexample, the second piezoelectric/electrostrictive element 24 b) towhich the negative level is applied. Accordingly, it is possible tofurther increase the displacement amount of the movable section 20. Inother words, when the waveforms indicated by the dashed lines in FIGS.15A and 15B are used, the device is allowed to have such a function thatthe piezoelectric/electrostrictive element 24 b or 24 a, to which thenegative level is applied, supports the piezoelectric/electrostrictiveelement 24 a or 24 b which principally makes the displacement action.

[0133] In the case of the piezoelectric/electrostrictive device 10Afshown in FIG. 7, the voltage (see the sine waveform Wa) shown in FIG.15A is applied, for example, to the piezoelectric/electrostrictiveelement 24 a 1 and the piezoelectric/electrostrictive element 24 b 2which are arranged on the diagonal line, and the voltage (see the sinewaveform Wb) shown in FIG. 15B is applied to the otherpiezoelectric/electrostrictive element 24 a 2 and the otherpiezoelectric/electrostrictive element 24 b 1.

[0134] As described above, in the piezoelectric/electrostrictive device10A according to the first embodiment, the minute displacement of thepiezoelectric/electrostrictive element 24 a, 24 b is amplified into thelarge displacement action by utilizing the bending of the thin platesection 16 a, 16 b, and it is transmitted to the movable section 20.Accordingly, it is possible to greatly displace the movable section 20with respect to the major axis m of the piezoelectric/electrostrictivedevice 10A.

[0135] Especially, in the first embodiment, the movable section 20 isprovided with the cutout 36 (through-hole 36 in this case) to realize alight weight of the movable section 20. Therefore, it is possible toincrease the resonance frequency without decreasing the displacementamount of the movable section 20.

[0136] The frequency herein indicates the frequency of the voltagewaveform obtained when the movable section 20 is displaced rightwardlyand leftwardly by alternately switching the voltage applied to the pairof electrodes 28, 30. The resonance frequency indicates the maximumfrequency at which the displacement action of the movable section 20 canfollow in a predetermined vibration mode.

[0137] In the piezoelectric/electrostrictive device 10A according to thefirst embodiment, the movable section 20, the thin plate sections 16 a,16 b, and the fixation section 22 are integrated into one unit. It isunnecessary that all of the parts are formed with the relatively fragileand heavy piezoelectric/electrostrictive material. Therefore, the devicehas the following advantages. That is, the device has a high mechanicalstrength, and it is excellent in handling performance, shock resistance,and moisture resistance. Further, the operation of the device isscarcely affected by harmful vibrations (for example, noise vibrationsand remaining vibrations during high speed operation).

[0138] In the first embodiment, the piezoelectric/electrostrictiveelement 24 a, 24 b is constructed to have thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 formed on both sides of the piezoelectric/electrostrictive layer 26.The first electrode 28 is formed on at least the outer surface of thethin plate section 16 a, 16 b. Therefore, the vibration caused by thepiezoelectric/electrostrictive element 24 a, 24 b can be efficientlytransmitted to the movable section 20 via the thin plate section 16 a,16 b. Thus, it is possible to improve the response performance.

[0139] In the first embodiment, the portion (substantial driving portion18), at which the pair of electrodes 28, 30 are overlapped with eachother with the piezoelectric/electrostrictive layer 26 interposedtherebetween, is continuously formed over the range from a part of thefixation section 22 to a part of the thin plate section 16 a, 16 b. Ifthe substantial driving portion 18 is formed to further extend over apart of the movable section 20, then it is feared that the displacementaction of the movable section 20 is restricted by the substantialdriving portion 18, and it is impossible to obtain the largedisplacement. However, in the first embodiment, the substantial drivingportion 18 is formed such that it does not range over both of themovable section 20 and the fixation section 22. Therefore, it ispossible to avoid the inconvenience of the restriction of thedisplacement action of the movable section 20, and it is possible toincrease the displacement amount of the movable section 20.

[0140] On the other hand, when the piezoelectric/electrostrictiveelement 24 a, 24 b is formed on the part of the movable section 20, itis preferable that the substantial driving portion 18 is located over arange from a part of the movable section 20 to a part of the thin platesection 16 a, 16 b, because of the following reason. That is, if thesubstantial driving portion 18 is formed to extend up to a part of thefixation section 22, the displacement action of the movable section 20is restricted as described above.

[0141] Next, explanation will be made for the preferred illustrativeconstructions of the piezoelectric/electrostrictive device 10A accordingto the first embodiment.

[0142] At first, in order to ensure the displacement action of themovable section 20, it is preferable that the distance g, by which thesubstantial driving portion 18 of the piezoelectric/electrostrictiveelement 24 a, 24 b is overlapped with the fixation section 22 or themovable section 20, is not less than ½ of the thickness d of the thinplate section 16 a, 16 b.

[0143] The device is constructed such that the ratio a/b between thedistance (distance in the X axis direction) a between the inner walls ofthe thin plate sections 16 a, 16 b and the width (distance in the Y axisdirection) b of the thin plate section 16 a, 16 b is 0.5 to 20. Theratio a/b is preferably 1 to 10 and more preferably 2 to 8. Theprescribed value of the ratio a/b is prescribed on the basis of thediscovery that the displacement amount of the movable section 20 can beincreased, and the displacement in the X-Z plane can be dominantlyobtained.

[0144] On the other hand, it is desirable that the ratio e/a between thelength (distance in the Z axis direction) e of the thin plate section 16a, 16 b and the distance a between the inner walls of the thin platesections 16 a, 16 b is preferably 0.5 to 10 and more preferably 0.7 to5. The prescribed value of the ratio e/a is prescribed on the basis ofthe discovery that the displacement amount of the movable section 20 canbe increased, and the displacement action can be performed at a highresonance frequency (high response speed can be achieved).

[0145] Therefore, in order to suppress the flapping displacement in theY axis direction or the vibration of the piezoelectric/electrostrictivedevice 10A according to the first embodiment and provide a structure inwhich a high speed response performance is excellent and a largedisplacement is simultaneously obtained at a relatively low voltage, itis preferable that the ratio a/b is 0.5 to 20 and the ratio e/a is 0.5to 10, and it is more preferable that the ratio a/b is 1 to 10 and theratio e/a is 0.7 to 5.

[0146] Further, it is preferable that the hole 12 is filled with a gelmaterial, for example, silicone gel. Usually, the displacement action ofthe movable section 20 is restricted by the presence of such a fillermaterial. However, in the first embodiment, it is intended to realizethe light weight brought about by the formation of the cutout 36 for themovable section 20 and increase the displacement amount of the movablesection 20. Therefore, the restriction of the displacement action of themovable section 20 due to the filler material is counteracted.Accordingly, it is possible to realize the effect owing to the presenceof the filler material, namely the realization of the high resonancefrequency and the maintenance of the rigidity.

[0147] It is preferable that the length (distance in the Z axisdirection) f of the movable section 20 is short, because of thefollowing reason. That is, it is possible to realize the light weightand increase the resonance frequency by shortening the length. However,in order to ensure the rigidity of the movable section 20 in the X axisdirection and obtain its reliable displacement, it is desirable that theratio f/d with respect to the thickness d of the thin plate section 16a, 16 b is not less than 3 and preferably not less than 10.

[0148] The actual size of each component is determined considering, forexample, the joining area for attaching the part to the movable section20, the joining area for attaching the fixation section 22 to anothermember, the joining area for attaching the electrode terminal or thelike, and the strength, the durability, the necessary displacementamount, the resonance frequency, and the driving voltage of the entirepiezoelectric/electrostrictive device 10A.

[0149] Specifically, for example, the distance a between the inner wallsof the thin plate sections 16 a, 16 b is preferably 100 μm to 2000 μmand more preferably 200 μm to 1000 μm. The width b of the thin platesection 16 a, 16 b is preferably 50 μm to 2000 μm and more preferably100 μm to 500 μm. The thickness d of the thin plate section 16 a, 16 bis preferably 2 μm to 100 μm and more preferably 4 μm to 50 μm, while itsatisfies b>d in relation to the width b of the thin plate section 16 a,16 b, in order to make it possible to effectively suppress the flappingdisplacement which is the displacement component in the Y axisdirection.

[0150] The length e of the thin plate section 16 a, 16 b is preferably200 μm to 3000 μm and more preferably 300 μm to 2000 μm. The length f ofthe movable section 20 is preferably 50 μm to 2000 μm and morepreferably 100 μm to 1000 μm.

[0151] The arrangement as described above exhibits such an extremelyexcellent effect that the displacement in the Y axis direction does notexceed 10% with respect to the displacement in the X axis direction,while the device can be driven at a low voltage by appropriately makingadjustment within the range of the size ratio and the actual size, andit is possible to suppress the displacement component in the Y axisdirection to be not more than 5%. In other words, the movable section 20is displaced in one axis direction, i.e., substantially in the X axisdirection. Further, the high speed response is excellent, and it ispossible to obtain a large displacement at a relatively low voltage.

[0152] In the piezoelectric/electrostrictive device 10A, the shape ofthe device is not a plate-shaped configuration (i.e., unlike aconventional device). Each of the movable section 20 and the fixationsection 22 has a rectangular parallelepiped-shaped configuration. Thepair of thin plate sections 16 a, 16 b are provided so that the sidesurface of the movable section 20 is continuous to the side surface ofthe fixation section 22. Therefore, it is possible to selectivelyincrease the rigidity of piezoelectric/electrostrictive device 10A inthe Y axis direction.

[0153] That is, in the piezoelectric/electrostrictive device 10A, it ispossible to selectively generate only the operation of the movablesection 20 in the plane (XZ plane). It is possible to suppress theoperation of the movable section 20 in the YZ plane (operation in theso-called flapping direction).

[0154] Next, explanation will be made for the respective constitutivecomponents of the piezoelectric/electrostrictive device 10A according tothe first embodiment.

[0155] As described above, the movable section 20 is the portion whichis operated on the basis of a driving amount of the thin plate section16 a, 16 b, and a variety of members are attached thereto depending onthe purpose of use of the piezoelectric/electrostrictive device 10A. Forexample, when the piezoelectric/electrostrictive device 10A is used as adisplacement element, a shield plate for an optical shutter or the likeis attached thereto. Especially, when the piezoelectric/electrostrictivedevice 10A is used for a mechanism for positioning a magnetic head of ahard disk drive or for suppressing a ringing, a member required to bepositioned is attached thereto, including, for example, the magnetichead, a slider provided with the magnetic head, and a suspensionprovided with the slider.

[0156] When the movable section 20 is constructed to have the cutout 36including the through-hole as shown in FIGS. 1 to 10, then the rigidityof the movable section 20 can be appropriately decreased, and thedisplacement in the X axis direction can be effectively increasedwithout increasing the flapping displacement (displacement in the Y axisdirection).

[0157] Further, a variety of members may be inserted and attached to thecutout 36 including the through-hole. Accordingly, an advantage isobtained such that the fixing and bonding area for the member can beincreased and the reliability of joining is enhanced, and/or anadvantage is obtained such that it is possible to make the thickness tobe thin or realize a small size of the piezoelectric/electrostrictivedevice attached with a variety of members.

[0158] As described above, the fixation section 22 is the portion forsupporting the thin plate sections 16 a, 16 b and the movable section20. For example, when the fixation section 22 is utilized to positionthe magnetic head of the hard disk drive, the entirepiezoelectric/electrostrictive device 10A is fixed by supporting andsecuring the fixation section 22, for example, to a carriage armattached to VCM (voice coil motor) or a fixation plate or a suspensionattached to the carriage arm. As shown in FIG. 1, the terminals 32, 34for driving the piezoelectric/electrostrictive elements 24 a, 24 b andother members are arranged on the fixation section 22 in some cases.

[0159] The material for constructing the movable section 20 and thefixation section 22 is not specifically limited provided that it hasrigidity. However, it is possible to preferably use ceramics to whichthe ceramic green sheet-laminating method is applicable as describedlater on. Specifically, the material includes, for example, materialscontaining a major component of zirconia represented by fully stabilizedzirconia and partially stabilized zirconia, alumina, magnesia, siliconnitride, aluminum nitride, and titanium oxide, as well as materialscontaining a major component of a mixture of them. However, in view of ahigh mechanical strength and a high toughness, it is preferable to use amaterial containing a major component of zirconia, especially fullystabilized zirconia and a material containing a major component ofpartially stabilized zirconia. The metal material is not limitedprovided that it has rigidity. However, the metal material includes, forexample, stainless steel and nickel.

[0160] As described above, the thin plate section 16 a, 16 b is aportion which is driven in accordance with the displacement of thepiezoelectric/electrostrictive element 24 a, 24 b. The thin platesection 16 a, 16 b is the thin plate-shaped member having flexibility,and it functions to amplify the expansion and contracting displacementof the piezoelectric/electrostrictive element 24 a, 24 b arranged on thesurface as the bending displacement and transmit the displacement to themovable section 20. Therefore, all that is required of the shape or thematerial of the thin plate section 16 a, 16 b is that it provides enoughflexibility and mechanical strength of such a degree that it is notbroken from the bending displacement action. It is possible to make theappropriate selection considering the response performance and theoperability of the movable section 20.

[0161] It is preferable that the thickness d of the thin plate section16 a, 16 b is preferably about 2 μm to 100 μm. it is preferable that thecombined thickness of the thin plate section 16 a (or 16 b) and thepiezoelectric/electrostrictive element 24 a (or 24 b) is 7 μm to 500 μm.It is preferable that the thickness of the electrode 28, 30 is 0.1 to 50μm, and the thickness of the piezoelectric/electrostrictive layer 26 is3 to 300 μm. The width b of the thin plate section 16 a, 16 b ispreferably 50 μm to 2000 μm.

[0162] Preferably, the thin plate sections 16 a and 16 b are fabricatedwith ceramic materials similar to those selected for use in the movablesection 20 and the fixation section 22. A material containing a majorcomponent of zirconia, especially fully stabilized zirconia and amaterial containing a major component of partially stabilized zirconiaare most preferably used, because the mechanical strength is large evenin the case of a thin wall thickness, the toughness is high, and thereactivity with the piezoelectric/electrostrictive layer and theelectrode material is small.

[0163] When the thin plate section 16 a, 16 b is made of a metalmaterial, it is enough that the metal material has flexibility and themetal material is capable of bending displacement as described above.However, preferably, it is desirable that the thin plate section 16 a,16 b is made of an iron-based material such as various stainless steelmaterials and various spring steel materials. Alternatively, it isdesirable that the thin plate section 16 a, 16 b is made of anon-ferrous material such as beryllium copper, phosphor bronze, nickel,and nickel-iron alloy.

[0164] Those which are fully stabilized or partially stabilized asfollows are preferably used as fully stabilized zirconia or partiallystabilized zirconia as described above. That is, the compound to be usedfor fully stabilizing or partially stabilizing zirconia includes yttriumoxide, ytterbium oxide, cerium oxide, calcium oxide, and magnesiumoxide. When at least one compound of them is added and contained,zirconia is partially or fully stabilized. However, as for thestabilization, the objective zirconia can be stabilized not only byadding one type of the compound but also by adding a combination of thecompounds.

[0165] The amount of addition of each of the compounds is desirably asfollows. That is, yttrium oxide or ytterbium oxide is added by 1 to 30mole %, preferably 1.5 to 10 mole %. Cerium oxide is added by 6 to 50mole %, preferably 8 to 20 mole %. Calcium oxide or magnesium oxide isadded by 5 to 40 mole %, preferably 5 to 20 mole %. Especially, it ispreferable to use yttrium oxide as a stabilizer. In this case, yttriumoxide is desirably added by 1.5 to 10 mole %, more preferably 2 to 4mole %. For example, alumina, silica, or transition metal oxide may beadded as an additive of sintering aid or the like in a range of 0.05 to20% by weight. However, when the sintering integration based on a filmformation method is adopted as a technique for forming thepiezoelectric/electrostrictive element 24 a, 24 b, it is also preferableto add, for example, alumina, magnesia, and transition metal oxide as anadditive.

[0166] In order to obtain the mechanical strength and the stable crystalphase, it is desirable that the average crystal grain size of zirconiais 0.05 to 3 μm, preferably 0.05 to 1 μm. As described above, ceramicscan be used for the thin plate section 16 a, 16 b in the same manner asin the movable section 20 and the fixation section 22. Preferably, it isadvantageous to construct the thin plate sections 16 a, 16 b with asubstantially identical material in view of the reliability of thejoined portion and the strength of the piezoelectric/electrostrictivedevice 10A, in order to reduce any complicated procedure of theproduction.

[0167] The piezoelectric/electrostrictive element 24 a, 24 b has atleast the piezoelectric/electrostrictive layer 26 and the pair ofelectrodes 28, 30 for applying the electric field to thepiezoelectric/electrostrictive layer 26. It is possible to use, forexample, piezoelectric/electrostrictive elements of the unimorph typeand the bimorph type. However, those of the unimorph type are suitablefor the piezoelectric/electrostrictive device 10A as described above,because they are excellent in stability of the generated displacementamount and they are advantageous to realize a light weight.

[0168] For example, as shown in FIG. 1, it is possible to preferablyuse, for example, the piezoelectric/electrostrictive element comprisingthe first electrode 28, the piezoelectric/electrostrictive layer 26, andthe second electrode 30 which are stacked in a layered configuration.Additionally, it is also preferable to provide a multiple stagestructure as shown in FIGS. 5 to 9.

[0169] As shown in FIG. 1, the piezoelectric/electrostrictive element 24a, 24 b is preferably formed on the outer surface side of thepiezoelectric/electrostrictive device 10A in view of the fact that thethin plate sections 16 a, 16 b can be driven to a greater extent.However, the piezoelectric/electrostrictive element 24 a, 24 b may beformed on the inner surface side of the piezoelectric/electrostrictivedevice 10A, i.e., on the inner wall surface of the hole 12 depending on,for example, the form of use. Alternatively, thepiezoelectric/electrostrictive elements 24 a, 24 b may be formed both onthe outer surface side and on the inner surface side of thepiezoelectric/electrostrictive device 10A.

[0170] A piezoelectric ceramic material is preferably used for thepiezoelectric/electrostrictive layer 26. However, it is also possible touse electrostrictive ceramics, ferroelectric ceramics, oranti-ferroelectric ceramics. However, when thepiezoelectric/electrostrictive device 10A is used, for example, toposition a magnetic head of a hard disk drive, it is important toprovide the linearity concerning the displacement amount of the movablesection 20 and the driving voltage or the output voltage. Therefore, itis preferable to use a material having small strain hysteresis. It ispreferable to use a material having a coercive electric field of notmore than 10 kV/mm.

[0171] Specified materials include ceramics containing, for example,lead zirconate, lead titanate, lead magnesium niobate, lead nickelniobate, lead zinc niobate, lead manganese niobate, lead antimonystannate, lead manganese tungstate, lead cobalt niobate, bariumtitanate, sodium bismuth titanate, potassium sodium niobate, andstrontium bismuth tantalate singly or in mixture.

[0172] Especially, a material containing a major component of leadzirconate, lead titanate, and lead magnesium niobate, or a materialcontaining a major component of sodium bismuth titanate is preferablyused, in order to obtain the product having a stable composition with ahigh electromechanical coupling factor and a piezoelectric constant andwith a small reactivity with the thin plate sections 16 a, 16 b(ceramics) during the sintering of the piezoelectric/electrostrictivelayer 26.

[0173] It is also preferable to use ceramics obtained by adding, to thematerial described above, for example, oxides of lanthanum, calcium,strontium, molybdenum, tungsten, barium, niobium, zinc, nickel,manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium,tantalum, lithium, bismuth, and stannum singly or in mixture.

[0174] For example, when lanthanum and/or strontium is contained in themajor components of lead zirconate, lead titanate, and lead magnesiumniobate, an advantage is obtained in some cases, for example, in such away that the coercive electric field and the piezoelectriccharacteristic can be adjusted.

[0175] It is desirable to avoid the addition of a material such assilica which tends to form glass, because of the following reason. Thatis, a material such as silica tends to react with thepiezoelectric/electrostrictive material during the heat treatment forthe piezoelectric/electrostrictive layer 26. As a result, thecomposition is varied, and the piezoelectric characteristic isdeteriorated.

[0176] On the other hand, it is preferable that the pair of electrodes28, 30 of the piezoelectric/electrostrictive element 24 a, 24 b are madeof metal which is solid at room temperature and which is excellent inconductivity. For example, it is possible to use metal simple substanceor alloy of, for example, aluminum, titanium, chromium, iron, cobalt,nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium,rhodium, silver, stannum, tantalum, tungsten, iridium, platinum, gold,and lead. It is also preferable to use a cermet material obtained bydispersing, in the metal described above, the same material as that ofthe piezoelectric/electrostrictive layer 26 or the thin plate section 16a, 16 b.

[0177] The material for the electrodes 28, 30 of thepiezoelectric/electrostrictive element 24 a, 24 b is selected anddetermined depending on the method for forming thepiezoelectric/electrostrictive layer 26. For example, when thepiezoelectric/electrostrictive layer 26 is formed by sintering on thefirst electrode 28 after the first electrode 28 is formed on the thinplate section 16 a, 16 b, it is necessary for the first electrode 28 touse high melting point metal such as platinum, palladium,platinum-palladium alloy, and silver-palladium alloy which does notchange at the sintering temperature for thepiezoelectric/electrostrictive layer 26. However, the electrodeformation can be performed at a low temperature for the second electrode30 which is formed on the piezoelectric/electrostrictive layer 26 afterforming the piezoelectric/electrostrictive layer 26. Therefore, it ispossible for the second electrode 30 to use low melting point metal suchas aluminum, gold, and silver.

[0178] The thickness of the electrode 28, 30 also serves as a factor toconsiderably decrease the displacement of thepiezoelectric/electrostrictive element 24 a, 24 b. Therefore, it ispreferable, especially for the electrode formed after the sintering ofthe piezoelectric/electrostrictive layer 26, to use organic metal pastecapable of obtaining a dense and thinner film after the sintering, forexample, a material such as gold resinate paste, platinum resinatepaste, and silver resinate paste.

[0179] Next, explanation will be made with reference to FIGS. 17A to 26for several methods for producing the piezoelectric/electrostrictivedevice 10A according to the first embodiment.

[0180] Ceramic materials are preferably used for the constitutivematerial for each of the members of the piezoelectric/electrostrictivedevice 10A according to the first embodiment. It is preferable that theconstitutive elements of the piezoelectric/electrostrictive device 10Aconcerning the substrate 14 except for thepiezoelectric/electrostrictive elements 24 a, 24 b, i.e., the thin platesections 16 a, 16 b, the fixation section 22, and the movable section 20are produced by using a ceramic green sheet-laminating method. On theother hand, it is preferable that the piezoelectric/electrostrictiveelements 24 a, 24 b as well as the respective terminals 32, 34 areproduced by using a film formation method, for example, for the thinfilm and the thick film.

[0181] According to the ceramic green sheet-laminating method in whichthe respective members of the substrate 14 of thepiezoelectric/electrostrictive device 10A can be formed in an integratedmanner, the time-dependent change of state scarcely occurs at the joinedportions of the respective members. Therefore, this method provides thehigh reliability of the joined portion, and it is advantageous to ensurethe rigidity.

[0182] In the piezoelectric/electrostrictive device 10A according to thefirst embodiment, the boundary portion (joined portion) between the thinplate section 16 a, 16 b and the fixation section 22 and the boundaryportion (joined portion) between the thin plate section 16 a, 16 b andthe movable section 20 function as supporting points for expressing thedisplacement. Therefore, the reliability of the joined portion is animportant point which dominates the characteristic of thepiezoelectric/electrostrictive device 10A.

[0183] The production methods described below are excellent inreproducibility and formability. Therefore, it is possible to obtain thepiezoelectric/electrostrictive device 10A having a predetermined shapewithin a short period of time with good reproducibility.

[0184] A first production method for the piezoelectric/electrostrictivedevice 10A according to the first embodiment will be specificallyexplained below. The following definitions are now made. The laminate,which is obtained by laminating the ceramic green sheets, is defined tobe the ceramic green laminate 58 (see, for example, FIG. 17B). Theintegrated matter, which is obtained by sintering the ceramic greenlaminate 58, is defined to be the ceramic laminate 60 (see, for example,FIG. 18). The integrated matter comprising the movable section 20, thethin plate sections 16 a, 16 b, and the fixation section 22, which isobtained by cutting off unnecessary portions from the ceramic laminate60, is defined to be the ceramic substrate 14C (see FIG. 19).

[0185] In the first production method, the ceramic laminate 60 isfinally cut into chip units to produce a large number ofpiezoelectric/electrostrictive devices 10A. However, in order tosimplify the explanation, description will be made principally for thecase in which one individual of piezoelectric/electrostrictive device10A is produced.

[0186] At first, for example, a binder, a solvent, a dispersing agent,and a plasticizer are added and mixed with a ceramic powder such aszirconia to prepare a slurry. The slurry is subjected to a degassingtreatment, and then a ceramic green sheet having a predeterminedthickness is prepared in accordance with, for example, a reverse rollcoater method and a doctor blade method.

[0187] Subsequently, the ceramic green sheet is processed into thosehaving various shapes as shown in FIG. 17A in accordance with, forexample, a method such as a punching out based on a die and a lasermachining method to obtain a plurality of ceramic green sheets 50A to50D, 52A, 52B for forming the substrate.

[0188] The ceramic green sheets 50A to 50D, 52A, 52B include theplurality (for example, four) of ceramic green sheets 50A to 50D each ofwhich is continuously formed with at least a window 54 for forming thehole 12 thereafter and a window 56 for forming the cutout (through-hole36) thereafter, and the plurality (for example, two) of ceramic greensheets 52A, 52B to be formed into the thin plate sections 16 a, 16 bthereafter. The numbers of ceramic green sheets referred to above arepersistently by way of example.

[0189] After that, as shown in FIG. 17B, the ceramic green sheets 50A to50D, 52A, 52B are stacked and secured under pressure so that the ceramicgreen sheets 50A to 50D are interposed between the ceramic green sheets52A, 52B to form a ceramic green laminate 58. Subsequently, the ceramicgreen laminate 58 is sintered to obtain a ceramic laminate 60 (see FIG.18).

[0190] It is noted that there is no limitation for the number ofpressure-securing process or processes and the sequence for the purposeof the laminating and integration into one unit. These factors can beappropriately determined depending on the structure, for example, sothat the desired structure is obtained on the basis of, for example, theshape of the windows 54, 56 and the number of ceramic green sheets.

[0191] It is unnecessary that the shape of the windows 54, 56 isidentical in all cases. The shape of the windows 54, 56 can bedetermined depending on the desired function. There is also nolimitation for the number of ceramic green sheets and the thickness ofeach of the ceramic green sheets.

[0192] In the pressure-securing process, it is possible to furtherimprove the laminating performance by applying the heat. The laminatingperformance at the boundary of the ceramic green sheet can be improvedby providing an auxiliary joining layer, for example, by applying andprinting, onto the ceramic green sheet, a paste or a slurry principallycontaining a ceramic powder (it is preferable to use a composition whichis the same as or similar to that of the ceramics used for the ceramicgreen sheet in order to ensure reliability), and a binder. When theceramic green sheets 52A, 52B are thin, it is preferable to handle themwith a plastic film, especially with a polyethylene terephthalate filmcoated with a releasing agent based on silicone on the surface.

[0193] Subsequently, as shown in FIG. 18, thepiezoelectric/electrostrictive elements 24 a, 24 b are formedrespectively on both surfaces of the ceramic laminate 60, i.e., on thesurfaces corresponding to the surfaces at which the ceramic green sheets52A, 52B are laminated. Those usable as the method for forming thepiezoelectric/electrostrictive elements 24 a, 24 b include a thick filmformation method such as a screen printing method, a dipping method, acoating method, and an electrophoresis method, and a thin film formationmethod such as an ion beam method, a sputtering method, a vacuum vapordeposition, an ion plating method, a chemical vapor deposition method(CVD), and a plating method.

[0194] When the piezoelectric/electrostrictive elements 24 a, 24 b areformed by using the film formation method as described above, thepiezoelectric/electrostrictive elements 24 a, 24 b and the thin platesections 16 a, 16 b can be integrally joined and arranged without usingany adhesive. It is possible to ensure the reliability and thereproducibility, and it is easy to form the stack.

[0195] In this case, it is preferable that thepiezoelectric/electrostrictive elements 24 a, 24 b are formed by meansof a thick film formation method, because of the following reason. Thatis, especially, when the piezoelectric/electrostrictive layer 26 isformed by using a thick film formation method, the film can be formed byusing, for example, a paste, a slurry, a suspension, an emulsion, or asol containing a major component of particles or powder of piezoelectricceramics having an average particle size of 0.01 to 5 μm, preferably0.05 to 3 μm. It is possible to obtain goodpiezoelectric/electrostrictive characteristics by sintering the formedfilm.

[0196] An electrophoresis method is advantageous in that the film can beformed at a high density with a high shape accuracy. A screen printingmethod is advantageous to simplify the production step, because it ispossible to simultaneously perform the film formation and the patternformation.

[0197] Explanation will be specifically made for the formation of thepiezoelectric/electrostrictive elements 24 a, 24 b. At first, theceramic green laminate 58 is sintered and integrated into one unit at atemperature of 1200° C. to 1600° C. to obtain the ceramic laminate 60.After that, the first electrodes 28 are printed and sintered atpredetermined positions on the both surfaces of the ceramic laminate 60.Subsequently, the piezoelectric/electrostrictive layers 26 are printedand sintered. Further, the second electrodes 30 are printed and sinteredto form the piezoelectric/electrostrictive elements 24 a, 24 b. Afterthat, the terminals 32, 34 are printed and sintered in order toelectrically connect the respective electrodes 28, 30 to the drivingcircuit.

[0198] In this process, when the materials are selected so that thesintering temperature for each of the members is lowered in accordancewith the stacking sequence, for example, when platinum (Pt) is used forthe first electrode 28, lead zirconate titanate (PZT) is used for thepiezoelectric/electrostrictive layer 26, gold (Au) is used for thesecond electrode 30, and silver (Ag) is used for the terminals 32, 34,then the material, which has been already sintered beforehand, is notrequired to be sintered again at a certain sintering stage. Thus, it ispossible to avoid the occurrence of inconvenience such as peeling offand aggregation of the electrode material or the like.

[0199] When the appropriate materials are selected, it is also possibleto successively print the respective members of thepiezoelectric/electrostrictive elements 24 a, 24 b and the terminals 32,34, followed by a one-time sintering. Further, it is also possible toprovide, for example, the respective electrodes 30 at a low temperatureafter forming the piezoelectric/electrostrictive layers 26.

[0200] Alternatively, the respective members of thepiezoelectric/electrostrictive elements 24 a, 24 b and the terminals 32,34 may be formed by means of a thin film formation method such as asputtering method and a vapor deposition method. In this case, it is notnecessarily indispensable to perform a heat treatment.

[0201] When the piezoelectric/electrostrictive elements 24 a, 24 b areformed, it is also preferable that the piezoelectric/electrostrictiveelements 24 a, 24 b are previously formed on both surfaces of theceramic green laminate 58, i.e., on the respective surfaces of theceramic green sheets 52A, 52B, and the ceramic green laminate 58 and thepiezoelectric/electrostrictive elements 24 a, 24 b are simultaneouslysintered or co-fired. For example, the following methods are availableto perform the co-firing. That is, the sintering may be performed forall of the constitutive films of the ceramic green laminate 58 and thepiezoelectric/electrostrictive elements 24 a, 24 b. The first electrodes28 and the ceramic green laminate 58 may be co-fired, or the otherconstitutive films (except for the second electrodes 30 and the ceramicgreen laminate 58) may be co-fired.

[0202] The following method is available to co-fire thepiezoelectric/electrostrictive elements 24 a, 24 b and the ceramic greenlaminate 58. That is, precursors of the piezoelectric/electrostrictivelayers 26 are formed, for example, in accordance with a tape formationmethod based on the use of a slurry material. The precursors of thepiezoelectric/electrostrictive layers 26 before the sintering arelaminated on the surfaces of the ceramic green laminate 58, for example,by means of a thermal securing process under pressure, followed by aco-firing to simultaneously produce the movable section 20, the thinplate sections 16 a, 16 b, the piezoelectric/electrostrictive layers 26,and the fixation section 22. However, in this method, it is necessary toform the electrodes 28 beforehand on the surfaces of the ceramic greenlaminate 58 or on the piezoelectric/electrostrictive layers 26 by usingthe film formation method described above.

[0203] Another method is also available. That is, the electrodes 28, 30and the piezoelectric/electrostrictive layers 26, which are therespective constitutive layers of the piezoelectric/electrostrictiveelements 24 a, 24 b, are formed by means of the screen printing onportions to be subsequently formed into at least the thin plate sections16 a, 16 b of the ceramic green laminate 58, followed by the co-firing.

[0204] The sintering temperature of the constitutive film of thepiezoelectric/electrostrictive element 24 a, 24 b is appropriatelydetermined depending on the material for constructing the same. However,the sintering temperature is generally 500° C. to 1500° C. The sinteringtemperature is preferably 1000° C. to 1400° C. for thepiezoelectric/electrostrictive layer 26. In this case, in order tocontrol the composition of the piezoelectric/electrostrictive layer 26,the sintering is preferably performed in the presence of an evaporationsource of the material of the piezoelectric/electrostrictive layer 26.When the piezoelectric/electrostrictive layers 26 and the ceramic greenlaminate 58 are co-fired, it is necessary to conform the sinteringconditions of the both. The piezoelectric/electrostrictive element 24 a,24 b is not necessarily formed on the both surfaces of the ceramiclaminate 60 or the ceramic green laminate 58. It is of course allowableto form the piezoelectric/electrostrictive element 24 a, 24 b on onlyone surface.

[0205] Subsequently, unnecessary portions are cut off from the ceramiclaminate 60 formed with the piezoelectric/electrostrictive elements 24a, 24 b as described above. The cutoff positions are located at sideportions of the ceramic laminate 60, especially at portions at which thehole 12 based on the window 54 is formed on the side surfaces of theceramic laminate 60 by means of the cutoff (see cutting lines C1 andC2), and at portions at which the through-hole 36 based on the window 56is formed at the portion of the movable section 20 of the ceramiclaminate 60 by means of the cutoff (see cutting line C3). As a result ofthe cutoff, as shown in FIG. 19, the piezoelectric/electrostrictivedevice 10A is completed, which comprises thepiezoelectric/electrostrictive elements 24 a, 24 b formed on the ceramicsubstrate 14C integrated with the movable section 20 formed with thethrough-hole 36 in the axial direction, the pair of thin plate sections16 a, 16 b, and the fixation section 22.

[0206] Those applicable as a cutoff method include a mechanicalmachining such as a dicing machining and a wire saw machining as well asan electron beam machining and a laser machining based on the use of,for example, the YAG laser and the excimer laser. It is preferable thatthe heat treatment is performed at 300° to 800° C. for thepiezoelectric/electrostrictive device 10A after the cutoff, because ofthe following reason. That is, any defect such as a microcrack tends tooccur in the device as a result of the machining, while the defect canbe removed by means of the heat treatment described above, and thereliability is improved. Further, it is preferable to apply the agingtreatment by being left to stand for at least 10 hours at a temperatureof about 80° C. after the heat treatment, because of the followingreason. That is, when the aging treatment is performed, for example, thevarious stresses, which have been exerted during the production process,can be mitigated to contribute to the improvement in devicecharacteristics.

[0207] The first embodiment described above is illustrative of the casein which the movable section 20, the fixation section 22, and the thinplate sections 16 a, 16 b are formed from a ceramic substrate material14C. Alternatively, each of the parts may be made of a metal material.Further alternatively, each of the parts may be made to provide a hybridstructure obtained by combining those produced with materials ofceramics and metals. In this case, in order to join the metal materialsto one another and/or join the ceramic and metal materials to oneanother, it is possible to use adhesion with organic resin or glass,brazing, soldering, eutectic bonding, or welding.

[0208] Explanation will be made with reference to FIGS. 20A to 26, forexample, for production methods (second and third production methods)for piezoelectric/electrostrictive devices(piezoelectric/electrostrictive devices 10Ak and 10Am according toeleventh and twelfth modified embodiments) having a hybrid structure inwhich the movable section 20 and the fixation section 22 are made ofceramic materials, and the thin plate sections 16 a, 16 b are made ofmetal materials. The substrate containing metal and ceramics, which isproduced by the second and third production methods, is referred to asthe substrate 14D.

[0209] In the second production method, at first, as shown in FIG. 20A,a plurality (for example, four) of frame-shaped ceramic green sheets 50Ato 50D each of which is continuously formed with at least a window 54for forming the hole 12 thereafter and a window 56 for forming thecutout (through-hole 36) thereafter are prepared.

[0210] After that, as shown in FIG. 20B, the ceramic green sheets 50A to50D are laminated and secured under pressure to form a ceramic greenlaminate 158. After that, as shown in FIG. 21A, the ceramic greenlaminate 158 is sintered to obtain a ceramic laminate 160. At thisstage, the ceramic laminate 160 is formed such that the hole 130 isformed by the windows 54, 56.

[0211] Subsequently, as shown in FIG. 21 B, thepiezoelectric/electrostrictive elements 24 a, 24 b, which areconstructed as separate members, are respectively bonded with an epoxyadhesive to the surfaces of metal plates 152A, 152B to serve as the thinplate sections. The separate members of thepiezoelectric/electrostrictive elements 24 a, 24 b can be formed, forexample, in accordance with the ceramic green sheet-laminating methodand the screen printing method.

[0212] Subsequently, the metal plates 152A, 152B are bonded to theceramic laminate 160 with the epoxy adhesive so that the ceramiclaminate 160 is interposed between the metal plates 152A, 152B and thehole 130 is closed thereby to provide a hybrid laminate 162 (see FIG.22).

[0213] Subsequently, as shown in FIG. 22, the hybrid laminate 162, whichis formed with the piezoelectric/electrostrictive elements 24 a, 24 b,is cut along cutting lines C1, C2, C3 to thereby cut off side portionsand forward end portions of the hybrid laminate 162. As a result of thecutoff, as shown in FIG. 23, the piezoelectric/electrostrictive device10Ak according to the eleventh modified embodiment is obtained, in whichthe piezoelectric/electrostrictive elements 24 a, 24 b are formed on thethin plate sections 16 a, 16 b constituted by the metal plates 152A,152B, of the substrate 14D, and the movable section 20 having thethrough-hole 36 is formed.

[0214] On the other hand, in the third production method, at first, aplurality (for example, four) of frame-shaped ceramic green sheets 50Ato 50D each of which is continuously formed with at least a window 54for forming the hole 12 thereafter and a window 56 for forming thecutout (through-hole 36) thereafter are prepared. The ceramic greensheets 50A to 50D are laminated and secured under pressure to form aceramic green laminate 158 (see FIGS. 20A and 20B).

[0215] After that, the ceramic green laminate 158 is sintered to obtaina ceramic laminate 160 as shown in FIG. 24A. At this stage, the ceramiclaminate 160 is formed such that the hole 130 is formed by the windows54, 56.

[0216] Subsequently, as shown in FIG. 24B, the metal plates 152A, 152Bare bonded to the ceramic laminate 160 with an epoxy adhesive so thatthe ceramic laminate 160 is interposed between the metal plates 152A,152B and the hole 130 is closed thereby to provide a hybrid laminate162. In this procedure, when the piezoelectric/electrostrictive elements24 a, 24 b are affixed to the surfaces of the bonded metal plates 152A,152B, the hole 130 is optionally filled with a filler material 164 asshown in FIG. 24A so that a sufficient pressure may be applied forbonding.

[0217] It is necessary to subsequently remove the filler material 164.Therefore, it is preferable to use a hard material which is easilydissolved in a solvent or the like. The material includes, for example,organic resin, wax, and brazing filler material. It is also possible toadopt a material obtained by mixing ceramic powder as a filler withorganic resin such as acrylic.

[0218] Subsequently, as shown in FIG. 25, thepiezoelectric/electrostrictive elements 24 a, 24 b, which areconstructed as separate members, are bonded with an epoxy adhesive tothe surfaces of the metal plates 152A, 152B of the hybrid laminate 162.The separate members of the piezoelectric/electrostrictive elements 24a, 24 b can be formed, for example, in accordance with a ceramic greensheet-laminating method and a screen printing method.

[0219] Subsequently, the hybrid laminate 162, which is formed with thepiezoelectric/electrostrictive elements 24 a, 24 b, is cut along cuttinglines C1, C2, C5 to thereby cut off side portions and forward endportions of the hybrid laminate 162. As a result of the cutoff, as shownin FIG. 26, the piezoelectric/electrostrictive device 10Am according tothe twelfth modified embodiment is obtained, in which thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on thethin plate sections 16 a, 16 b constituted by the metal plates 152A,152B, of the substrate 14D, and the movable section 20 having thethrough-hole 36 is formed.

[0220] When all of the substrate section is made of metal, for example,the portions corresponding to the ceramic laminate 160 shown in FIG. 21Aare formed by means of molding. Further, thin metal materials may belaminated to form the substrate section in accordance with a claddingmethod.

[0221] Next, explanation will be made for apiezoelectric/electrostrictive device 10B according to the secondembodiment with reference to FIGS. 27 to 30. Components or partscorresponding to those shown in FIG. 1 are designated by the samereference numerals, duplicate explanation of which will be omitted.

[0222] As shown in FIG. 27, the piezoelectric/electrostrictive device10B according to the second embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above. However, the formeris different from the latter in that the movable section 20 isconstructed to have an empty vessel structure. Specifically, the insideof the movable section 20 is hollow (hollow section 70), and the forwardend thereof is a closed surface 72. For example, a rectangularthrough-hole 74 is formed on the side wall.

[0223] Also in the piezoelectric/electrostrictive device 10B accordingto the second embodiment, the movable section 20 is allowed to have alight weight, in the same manner as in thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above. Therefore, it is possible to increase theresonance frequency without decreasing the displacement amount of themovable section 20.

[0224] The hollow section 70 and the through-hole 74 are formed for themovable section 20. Accordingly, the rigidity of the movable section 20can be appropriately lowered, and the displacement in the X axisdirection can be effectively increased without increasing the flappingdisplacement (displacement in the Y axis direction).

[0225] Further, a variety of members may be inserted and attached to thehollow section 70 and the through-hole 74. Accordingly, an advantage is,obtained such that the fixing and bonding area for the member can beincreased and the reliability of joining is enhanced, and/or anadvantage is obtained such that it is possible to make the thickness tobe thin or realize a small size of the piezoelectric/electrostrictivedevice 10B attached with a variety of members.

[0226] The effect to realize the high resonance frequency, which isbrought about by the realization of the light weight of thepiezoelectric/electrostrictive device 10B according to the secondembodiment, is of a somewhat lower nature with respect to that of thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above. However, the mechanical strength isexcellent. Therefore, an advantage is obtained such that the degree offreedom is high when a variety of members or parts are attached to themovable section 20, and it is easy to perform the design.

[0227] The same steps as those executed in the method for producing thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above are also executed when thepiezoelectric/electrostrictive device 10B according to the secondembodiment is produced.

[0228] A production method, which follows the first production methoddescribed above, will be explained below. At first, as shown in FIG.28A, for example, a method such as a punching out based on a die or alaser machining is used to prepare a plurality (for example, four) ofceramic green sheets 50A to 50D continuously formed with at least awindow 54 for forming the hole 12 thereafter and a window 80 for formingthe hollow section 70 thereafter, and a plurality (for example, two) ofceramic green sheets 52A, 52B for forming the thin plate sections 16 a,16 b thereafter, having the through-hole 74 at a portion correspondingto the window 80.

[0229] After that, as shown in FIG. 28B, the ceramic green sheets 50A to50D, 52A, 52B are laminated and secured under pressure so that theceramic green sheets 50A to 50D are interposed between the ceramic greensheets 52A, 52B to provide a ceramic green laminate 58. After that, asshown in FIG. 29, the ceramic green laminate 58 is sintered to obtain aceramic laminate 60.

[0230] After that, as shown in FIG. 29, thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on bothsurfaces of the ceramic laminate 60, i.e., on surfaces corresponding tothe surfaces at which the ceramic green sheets 52A, 52B are laminated.

[0231] Subsequently, unnecessary portions are cut off from the ceramiclaminate 60 which is formed with the piezoelectric/electrostrictiveelements 24 a, 24 b as described above. The cutoff is performed atpositions corresponding to side portions of the ceramic laminate 60,especially portions at which the hole 12 based on the window 54 isformed at the side surface of the ceramic laminate 60 by the cutoff (seecutting lines C1 and C2), and a portion at which the hollow section 70based on the window 80 is formed at the portion of the movable section20 of the ceramic laminate 60 (see cutting line C4). As a result of thecutoff, as shown in FIG. 30, the piezoelectric/electrostrictive device10B is completed, in which the piezoelectric/electrostrictive elements24 a, 24 b are formed on a ceramic substrate 14C integrated with themovable section 20 formed with the hollow section 70 and thethrough-hole 74, the pair of thin plate sections 16 a, 16 b, and thefixation section 22.

[0232] The embodiment described above is illustrative of the case tofollow the first production method. Alternatively, thepiezoelectric/electrostrictive device 10B may be produced in accordancewith the second production method or the third production method basedon the use of the metal plates 152A, 152B.

[0233] Next, explanation will be made for apiezoelectric/electrostrictive device 10C according to the thirdembodiment with reference to FIG. 31. Components or parts correspondingto those shown in FIG. 1 are designated by the same reference numerals,duplicate explanation of which will be omitted.

[0234] As shown in FIG. 31, the piezoelectric/electrostrictive device10C according to the third embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above. However, the formeris different from the latter in that a portion of the movable section20, which corresponds to the principal surface disposed oppositely tothe front surface 20 b, is eliminated, and the movable section 20 is cutoff to a great extent (cutout 120).

[0235] In this embodiment, the thickness h of the side surface 20c ofthe movable section 20 is the same as the thickness d of the thin platesections 16 a, 16 b.

[0236] The piezoelectric/electrostrictive device 10C according to thethird embodiment is also formed with the cutout 120, and thus themovable section 20 is allowed to have a light weight, in the same manneras the piezoelectric/electrostrictive device 10A according to the firstembodiment. Therefore, it is possible to increase the resonancefrequency without decreasing the displacement amount of the movablesection 20. Especially, in the third embodiment, the weight can begreatly reduced. Therefore, it is possible to increase the areal size ofthe entire piezoelectric/electrostrictive device 10C or the movablesection 20. It is possible to improve the degree of freedom concerningthe attachment of a variety of members or parts.

[0237] The cutout 120 is formed for the movable section 20. Accordingly,the rigidity of the movable section 20 can be appropriately lowered, andthe displacement in the X axis direction can be effectively increasedwithout increasing the flapping displacement (displacement in the Y axisdirection).

[0238] When a variety of members or parts are attached, then the memberor the part may be fixed in a form of being fitted on the side of thecutout 120, or it may be fixed on the back surface side thereof, i.e.,on the side of the front surface 20 b of the movable section 20. Whenthe fixation is effected on the side of the cutout 120, there isobtained an advantage that the thickness of thepiezoelectric/electrostrictive device 10C attached with the member orthe part can be made thin, and an advantage that the fixing area for themember or the part can be enlarged.

[0239] The strength of the structure is lowered as compared with thepiezoelectric/electrostrictive device 10A according to the firstembodiment. Therefore, it is preferable that the thickness i of thefront surface 20 b of the movable section 20 is made thicker than thatin the first embodiment.

[0240] When the piezoelectric/electrostrictive device 10C according tothe third embodiment is produced, the same steps as those used in theproduction method for the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above are executed. However,explanation therefor is omitted.

[0241] A partition 38 may be provided between the cutout 120 and thehole 12, as in a piezoelectric/electrostrictive device 10Ca according toa modified embodiment shown in FIG. 32. In this case, when a variety ofmembers or parts are inserted into the cutout 36 to be fixed, the memberor the part can be easily positioned by the aid of the partition 38. Itis possible to reduce the dispersion of the characteristic of the finalproduct. Further, it is possible to utilize the four or five surfaces asthe bonding and fixing surfaces. Thus, the reliability is improved forthe attachment of the member or the part.

[0242] Next, explanation will be made for apiezoelectric/electrostrictive device 10D according to the fourthembodiment with reference to FIGS. 33 to 36. Components or partscorresponding to those shown in FIG. 31 are designated by the samereference numerals, duplicate explanation of which will be omitted.

[0243] As shown in FIG. 33, the piezoelectric/electrostrictive device10D according to the fourth embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Caccording to the third embodiment described above. However, the formeris different from the latter in that the front surface 20 b of themovable section 20 is located at an approximately central position inthe widthwise direction of the movable section 20 to construct asubstantially H-shaped upper surface. That is, thepiezoelectric/electrostrictive device 10D is constructed such thatcutouts 90, 92 are provided for both principal surfaces of the movablesection 20 respectively.

[0244] Also in the piezoelectric/electrostrictive device 10D accordingto the fourth embodiment, the movable section 20 is allowed to have alight weight, in the same manner as in thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above. Therefore, it is possible to increase theresonance frequency without decreasing the displacement amount of themovable section 20.

[0245] Especially, the piezoelectric/electrostrictive device 10Daccording to the fourth embodiment has such a form that the sidesurfaces 20 c of the movable section 20 are connected via the frontsurface 20 b at positions symmetrical to one another in the widthwisedirection. Therefore, a feature is obtained such that the flapping isdecreased in the Y axis direction, as the displacement form.

[0246] When the front surface 20 b, which is formed at the deepposition, is utilized as an attachment surface for a variety of membersor parts, then the member or the part is attached so that it is fitted,and the member or the part can be supported with the three surfaces ofthe back surface of the front surface 20 b and the pair of inner wallsurfaces of the side surfaces 20 c of the movable section 20. Therefore,it is possible to reliably hold a part which is larger than the movablesection 20.

[0247] In other words, the cutouts 90, 92 are formed for the movablesection 20. Accordingly, the rigidity of the movable section 20 can beappropriately lowered, and the displacement in the X axis direction canbe effectively increased without increasing the flapping displacement(displacement in the Y axis direction).

[0248] When a variety of members or parts are attached, then the memberor the part may be fixed in a form of being fitted to the cutout 90, 92.In this case, there are obtained an advantage that the thickness of thepiezoelectric/electrostrictive device 10D attached with the member orthe part can be made thin, and an advantage that the fixing area for themember or the part can be enlarged.

[0249] The same steps as those executed in the method for producing thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above are also executed when thepiezoelectric/electrostrictive device 10D according to the fourthembodiment is produced.

[0250] A production method, which follows the first production methoddescribed above, will be explained below. At first, as shown in FIG.34A, for example, a method such as the punching out based on a die or alaser machining is used to prepare a plurality (for example, four) ofceramic green sheets 50A to 50D continuously formed with at least awindow 54 for forming the hole 12 thereafter and windows 100, 102 forforming the cutouts 90, 92 thereafter, and a plurality (for example,two) of ceramic green sheets 52A, 52B for forming the thin platesections 16 a, 16 b thereafter.

[0251] After that, as shown in FIG. 34B, the ceramic green sheets 50A to50D, 52A, 52B are laminated and secured under pressure so that theceramic green sheets 50A to 50D are interposed between the ceramic greensheets 52A, 52B to provide a ceramic green laminate 58. After that, asshown in FIG. 35, the ceramic green laminate 58 is sintered to obtain aceramic laminate 60.

[0252] After that, as shown in FIG. 35, thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on bothsurfaces of the ceramic laminate 60, i.e., on surfaces corresponding tothe surfaces at which the ceramic green sheets 52A, 52B are laminated.

[0253] Subsequently, unnecessary portions are cut off from the ceramiclaminate 60 which is formed with the piezoelectric/electrostrictiveelements 24 a, 24 b as described above. The cutoff is performed atpositions corresponding to side portions of the ceramic laminate 60,especially portions at which the hole 12 based on the window 54 isformed at the side surface of the ceramic laminate 60 by the cutoff (seecutting lines C1 and C2), and a portion at which the cutouts 90, 92based on the windows 100,102 are formed at the portions of the movablesection 20 of the ceramic laminate 60 (see cutting line C3). As a resultof the cutoff, as shown in FIG. 36, the piezoelectric/electrostrictivedevice 10D is completed, in which the piezoelectric/electrostrictiveelements 24 a, 24 b are formed on a ceramic substrate 14C integratedwith the movable section 20 having the substantially H-shaped uppersurface, the pair of thin plate sections 16 a, 6 b, and the fixationsection 22.

[0254] Next, explanation will be made for apiezoelectric/electrostrictive device 10E according to the fifthembodiment with reference to FIG. 37. Components or parts correspondingto those shown in FIG. 31 are designated by the same reference numerals,duplicate explanation of which will be omitted.

[0255] As shown in FIG. 37, the piezoelectric/electrostrictive device10E according to the fifth embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Caccording to the third embodiment described above (see FIG. 31).However, the former is different from the latter in that a portion ofthe side surface 20 c of the movable section 20 is partially eliminated.In other words, the movable section 20 is constructed by only a portionof the front surface 20 b.

[0256] Also in the piezoelectric/electrostrictive device 10E accordingto the fifth embodiment, the movable section 20 is allowed to have alight weight, in the same manner as in thepiezoelectric/electrostrictive device 10A according to the firstembodiment. Therefore, it is possible to increase the resonancefrequency without decreasing the displacement amount of the movablesection 20. Especially, in the fifth embodiment, the movable section 20is constructed by only the minimum portion necessary to attach the part.Therefore, even when the areal size is enlarged in order to attach thepart, it is possible to suppress the increase in mass of the movablesection 20 to a minimum. Accordingly, the piezoelectric/electrostrictivedevice 10E according to the fifth embodiment is most suitable to realizea high resonance frequency.

[0257] That is, the movable section 20 is constructed by only a portionof the front surface 20 b. Accordingly, the rigidity of the movablesection 20 can be appropriately lowered, and the displacement in the Xaxis direction can be effectively increased without increasing theflapping displacement (displacement in the Y axis direction).

[0258] A variety of members or parts may be attached on the back surfaceside of a portion of the front surface 20 b. In this case, there isobtained an advantage that the thickness of thepiezoelectric/electrostrictive device 10E attached with the member orthe part can be made thin, and an advantage that the member or the partcan be fixed to be fitted into the hole 12, and thus it is possible torealize a small size of the piezoelectric/electrostrictive device 10Eattached with the member or the part.

[0259] When the piezoelectric/electrostrictive device 10E according tothe fifth embodiment is produced, the same steps as those used in theproduction method for the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above are executed. However,explanation therefor is omitted.

[0260] Next, explanation will be made for apiezoelectric/electrostrictive device 10F according to the sixthembodiment with reference to FIGS. 38 to 42. Components or partscorresponding to those shown in FIG. 1 are designated by the samereference numerals, duplicate explanation of which will be omitted.

[0261] As shown in FIG. 38, the piezoelectric/electrostrictive device10F according to the sixth embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above. However, the formeris different from the latter in that the movable section 20 is solidwithout involving, for example, the hollow section and the through-hole,and a part of the inner wall 20 a of the movable section 20 is expandedin the hole 12 (expanded section 110). In other words, thepiezoelectric/electrostrictive device 10F is constructed such that theareal size of the front surface 20 b of the movable section 20 isincreased owing to the presence of the expanded section 110.

[0262] In the piezoelectric/electrostrictive device 10F according to thesixth embodiment, for example, when a variety of members or parts areattached to the front surface 20 b of the movable section 20, it ispossible to increase the areal size of the front surface 20 b(attachment surface for the member or the part in this case) of themovable section 20, without changing the maximum length of thepiezoelectric/electrostrictive device 10F.

[0263] In this embodiment, the weight is increased due to the provisionof the expanded section 110. However, the expanded section 110 isexpanded toward the hole 12. Therefore, the center of gravity of themovable section 20 can be located at a position deviated toward thefixation section 22. Little influence is exerted by the decrease inresonance frequency brought about by the increase in weight. In thisembodiment, the member or the part is attached at a position deviatedtoward the fixation section 22 as well. Therefore, the resonancefrequency is scarcely decreased after attaching the member or the part,and the displacement of the movable section 20 is maintained asintended. In other words, the piezoelectric/electrostrictive device 10Fis designed such that the resonance frequency is substantially improved.

[0264] In other words, in the piezoelectric/electrostrictive device 10Faccording to the sixth embodiment, the areal size of the attachmentsurface for the member or the part is increased for the movable section20, and the reliability is improved concerning the attachment of themember or the part, while the degree of influence on the resonancefrequency (decrease in resonance frequency) can be decreased, whichwould be otherwise caused when the attachment of the member or the partis considered to be important.

[0265] The same steps as those executed in the method for producing thepiezoelectric/electrostrictive device 10A according to the firstembodiment described above are also executed when thepiezoelectric/electrostrictive device 10F according to the sixthembodiment is produced.

[0266] A production method, which follows the first production methoddescribed above, will be explained below. At first, as shown in FIG.39A, for example, a method such as the punching out based on a die or alaser machining is used to prepare a plurality (for example, four) offirst ceramic green sheets 50A to 50D having at least a window 54 forforming the hole 12 thereafter and a projection 112 protruding towardthe inside of the window 54 for forming the expanded section 110thereafter, a plurality (for example, two) of second ceramic greensheets 116A, 16B formed with a window 114 for forming the hole 12thereafter, and a plurality (for example, two) of ceramic green sheets52A, 52B for forming the thin plate sections 16 a, 16 b thereafter.

[0267] After that, as shown in FIG. 39B, the first ceramic green sheets50A to 50D are laminated and secured under pressure so that an obtainedlaminate (laminate of the first ceramic green sheets 50A to 50D) isinterposed between the second ceramic green sheets 116A, 116B. Further,the first and second ceramic green sheets 50A to 50D, 116A, 116B arelaminated and secured under pressure so that they are interposed betweenthe ceramic green sheets 52A, 52B to thereby provide a ceramic greenlaminate 58. After that, as shown in FIG. 40, for example, the ceramicgreen laminate 58 is sintered to obtain a ceramic laminate 60.

[0268] After that, as shown in FIG. 41, thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on bothsurfaces of the ceramic laminate 60, i.e., on surfaces corresponding tothe surfaces at which the ceramic green sheets 52A, 52B are laminated.

[0269] Subsequently, unnecessary portions are cut off from the ceramiclaminate 60 which is formed with the piezoelectric/electrostrictiveelements 24 a, 24 b as described above. The cutoff is performed atpositions corresponding to side portions of the ceramic laminate 60,especially portions at which the hole 12 based on the window 54 isformed at the side surface of the ceramic laminate 60 by the cutoff (seecutting lines C1 and C2). As a result of the cutoff, as shown in FIG.41, the piezoelectric/electrostrictive device 10F is completed, in whichthe piezoelectric/electrostrictive elements 24 a, 24 b are formed on aceramic substrate 14C integrated with the movable section 20 having theexpanded section 110 expanded toward the hole 12, the pair of thin platesections 16 a, 16 b, and the fixation section 22.

[0270] In this embodiment, the movable section 20 is constructed to besolid. Alternatively, as in a piezoelectric/electrostrictive device 10Faaccording to a modified embodiment shown in FIG. 42, various cutouts 36(for example, the through-hole and the hollow section) may be provided,or the device may be constructed to have an empty vessel structure or aplate-shaped configuration with only a part attachment surface. In thiscase, it is advantageous to realize a high resonance frequency, becausethe movable section 20 is allowed to have a light weight. Thepiezoelectric/electrostrictive device 10Fa according to this modifiedembodiment is illustrative of the case in which a through-hole 36 havinga rectangular cross section, which is continuously formed over a rangefrom the forward end surface of the movable section 20 to the hole 12,is formed for the movable section 20 which is provided with the expandedsection 110 expanded toward the hole 12.

[0271] Next, explanation will be made for apiezoelectric/electrostrictive device 10G according to the seventhembodiment with reference to FIG. 43. Components or parts correspondingto those shown in FIG. 1 are designated by the same reference numerals,duplicate explanation of which will be omitted.

[0272] As shown in FIG. 43, the piezoelectric/electrostrictive device10G according to the seventh embodiment is constructed in approximatelythe same manner as the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above. However, the formeris different from the latter in that the areal size of the front surface20 b of the movable section 20 is widened in the lateral direction(direction of the X axis).

[0273] In this case, when the front surface of the movable section 20 isutilized as an attachment surface for a variety of members or parts, itis possible to improve the reliability concerning the attachment of themember or the part, because the areal size of the front surface 20 b iswidened. The front surface 20 b may be produced in an integrated manner,for example, in accordance with a green sheet-laminating method, or itmay be bonded as a separate member afterward. In this case, there is nospecial limitation for the material such as a metal and ceramics.

[0274] The piezoelectric/electrostrictive devices 10A to 10G accordingto the first to seventh embodiments are illustrative of the individualadoption of the arrangement in which the movable section 20 is allowedto have the light weight (first to fifth embodiments), the arrangementin which the expanded section 110 protruding from the movable section 20to the hole 12 is provided (sixth embodiment), and the arrangement inwhich the areal size of the front surface 20 b of the movable section 20is widened in the lateral direction (seventh embodiment) respectively.Alternatively, it is also preferable to combine the arrangement in whichthe movable section 20 is allowed to have a light weight and thearrangement in which the expanded section 110 protruding from themovable section 20 to the hole 12 is provided. In this case, it ispossible to simultaneously realize the high resonance frequency owing tothe light weight of the movable section 20 and the reliability of theattachment of the part, as well as the suppression of the decrease inresonance frequency owing to the fact that the attachment position forthe member or the part can be shifted toward the fixation side.

[0275] It is also preferable to combine the arrangement in which theexpanded section 110 protruding from the movable section 20 to the hole12 is provided and the arrangement in which the areal size of the frontsurface 20 b of the movable section 20 is widened in the lateraldirection. In this case, it is possible to simultaneously realize thereliability of the attachment of the part and the increase indisplacement amount of the movable section 20, as well as thesuppression of the decrease in resonance frequency owing to the factthat the attachment position for the member or the part can be shiftedtoward the fixation side.

[0276] Further, it is also preferable to combine all of the arrangementsdescribed above. In this case, it is possible to simultaneously realizea high resonance frequency owing to the light weight of the movablesection 20, the increase in displacement amount of the movable section20, and the reliability of the attachment of the part, as well as thesuppression of the decrease in resonance frequency owing to the factthat the attachment position for the member or the part can be shiftedtoward the fixation side.

[0277] The piezoelectric/electrostrictive device described above can beutilized as the active device including, for example, varioustransducers, various actuators, frequency region functional parts(filters), transformers, vibrators, resonators, oscillators, anddiscriminators for the communication and the power generation, as wellas the sensor element for various sensors including, for example,ultrasonic sensors, acceleration sensors, angular velocity sensors,shock sensors, and mass sensors. Especially, thepiezoelectric/electrostrictive device described above can be preferablyutilized for various actuators to be used as the mechanism for adjustingthe displacement and the positioning and for adjusting the angle forvarious precision parts such as those of optical instruments andprecision mechanical equipments.

[0278] It is a matter of course that the piezoelectric/electrostrictivedevice and the method for producing the same according to the presentinvention are not limited to the embodiments described above, which maybe embodied in other various forms without deviating from the gist oressential characteristics of the present invention.

1. A method for producing a piezoelectric/electrostrictive devicecomprising: a pair of mutually opposing thin plate sections, a movablesection, and a fixation section for supporting said thin plate sectionsand said movable section; one or more piezoelectric/electrostrictiveelements arranged on at least one thin plate section of said pair ofthin plate sections; and a hole formed by both inner walls of said pairof thin plate sections, an inner wall of said movable section, and aninner wall of said fixation section, said method comprising: a step offorming said movable section having a cutout by cutting off apredetermined part after producing at least saidpiezoelectric/electrostrictive element on said thin plate section. 2.The method for producing said piezoelectric/electrostrictive deviceaccording to claim 1, wherein said cutout includes a hollow sectionand/or a through-hole provided for said movable section.
 3. A method forproducing a piezoelectric/electrostrictive device comprising: a pair ofmutually opposing thin plate sections, a movable section, and a fixationsection for supporting said thin plate sections and said movablesection; one or more piezoelectric/electrostrictive elements arranged onat least one thin plate section of said pair of thin plate sections; anda hole formed by both inner walls of said pair of thin plate sections,an inner wall of said movable section, and an inner wall of saidfixation section; said method comprising: a step of producing a ceramiclaminate by integrally sintering a ceramic green laminate including atleast a ceramic green sheet having a window for forming at least saidhole thereafter and ceramic green sheets to be formed into said thinplate sections thereafter to produce said ceramic laminate; a step offorming said piezoelectric/electrostrictive element on an outer surfaceof a portion of said ceramic laminate to be formed into said thin platesection; and a cutoff step of forming said movable section having atleast a cutout by means of at least one time of cutoff treatment forsaid ceramic laminate formed with said piezoelectric/electrostrictiveelement.
 4. The method for producing said piezoelectric/electrostrictivedevice according to claim 3, wherein: in said step of producing saidceramic laminate, said ceramic laminate is produced by integrallysintering a ceramic green laminate including a ceramic green sheethaving a window for forming said movable section having at least saidcutout, and said ceramic green sheets to be formed into said thin platesections thereafter to produce said ceramic laminate; and in said cutoffstep, said movable section having at least said cutout is formed bymeans of said cutoff treatment for said ceramic laminate formed withsaid piezoelectric/electrostrictive element.
 5. The method for producingsaid piezoelectric/electrostrictive device according to claim 3, whereinsaid cutout includes a hollow section and/or a through-hole provided forsaid movable section.
 6. The method for producing saidpiezoelectric/electrostrictive device according to claim 3, wherein insaid cutoff step, said hole is exposed by means of said cutoff treatmentfor said ceramic laminate.
 7. A method for producing apiezoelectric/electrostrictive device comprising: a pair of mutuallyopposing thin plate sections, a movable section, and a fixation sectionfor supporting said thin plate sections and said movable section; one ormore piezoelectric/electrostrictive elements arranged on at least onethin plate section of said pair of thin plate sections; and a holeformed by both inner walls of said pair of thin plate sections, an innerwall of said movable section, and an inner wall of said fixationsection, said method comprising: a step of forming said movable sectionhaving an expanded section expanded in said hole by cutting off apredetermined part after producing at least saidpiezoelectric/electrostrictive element on said thin plate section.
 8. Amethod for producing a piezoelectric/electrostrictive device comprising:a pair of mutually opposing thin plate sections, a movable section, anda fixation section for supporting said thin plate sections and saidmovable section; one or more piezoelectric/electrostrictive elementsarranged on at least one thin plate section of said pair of thin platesections; and a hole formed by both inner walls of said pair of thinplate sections, an inner wall of said movable section, and an inner wallof said fixation section; said method comprising: a step of producing aceramic laminate by integrally sintering a ceramic green laminateincluding at least a ceramic green sheet having a window for forming atleast said hole thereafter and ceramic green sheets to be formed intosaid thin plate sections thereafter to produce said ceramic laminate; astep of forming said piezoelectric/electrostrictive element on an outersurface of a portion of said ceramic laminate to be formed into saidthin plate section; and a cutoff step of forming said movable sectionhaving at least an expanded section expanded in said hole by means of atleast one time of cutoff treatment for said ceramic laminate formed withsaid piezoelectric/electrostrictive element.
 9. The method for producingsaid piezoelectric/electrostrictive device according to claim 7,wherein: in said step of producing said ceramic laminate, said ceramiclaminate is produced by integrally sintering a ceramic green laminateincluding a ceramic green sheet having a window for forming said movablesection formed with at least said expanded section, and said ceramicgreen sheets to be formed into said thin plate sections thereafter toproduce said ceramic laminate; and in said cutoff step, said movablesection having at least said expanded section is formed by means of saidcutoff treatment for said ceramic laminate formed with saidpiezoelectric/electrostrictive element.
 10. The method for producingsaid piezoelectric/electrostrictive device according to claim 7, whereinin said cutoff step, said hole is exposed by means of said cutofftreatment for said ceramic laminate.